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ASNT Research Symposium 2019

ASNT Research Symposium 2019

Hyatt Regency Orange CountyGarden Grove, CA

1 - 4 April 2019

ASNT Research Symposium is one of the premier platforms for exchanging information on groundbreaking, trending and emerging research, technology transfer and engineering practices in the field of nondestructive evaluation (NDE). During the Symposium, you will have numerous opportunities to explore, discuss and share your experiences on cutting edge NDE technologies—from research level to real-world application.

On behalf of the organizing committee, we would like to extend a warm invitation to you and your colleagues to participate in the ASNT Research Symposium in 2019.

Dr Charles Kuehmann

Keynote - Reusable Spacecraft and NDE

Presenting author(s):
Dr Charles Kuehmann

Co-Authors:

Room: Grand E-F Ballroom | 8:00 AM Tuesday, April 2, 2019

SpaceX is a private Space transportation service provider that designs, manufactures and launches advanced rockets and spacecraft. The company was founded in 2002 to revolutionize space technology, with the ultimate goal of enabling people to live on other planets.

Fully reusable spacecraft are a key component to the strategy to cost effective transport to Mars and other bodies beyond earth orbit. Understanding the role of flaws in materials and components, and their propagation during service is a key factor in designing and building safe space vehicles. At SpaceX, we have a unique opportunity as the Nondestructive testing specialists to understand the engineering and manufacturing behind the product so that we can custom design and implement the most efficient and reliable inspection for our spacecraft.

Understanding of the materials and manufacturing processes also gives us insight into the natural locations that inherent defects might appear and the optimum methods of detection. There is a requirement for practicality and conservation of resources as a private commercial entity in order to keep the company profitable while ensuring the highest quality of product.

SpaceX has adopted the latest inspection technologies as we look to optimize detection capability, and reduce inspection times and increase throughput with robots and automation. One example of advanced automation is our fully automated through transmission air scan ultrasonic robot used for inspection of our composite fairings. Each fairing is similar in size to a city bus.

At SpaceX, NDE is optimally integrated with Materials Engineering to collaborate between our engineering and technical specialties to enhance technical capability. NDE development occurs in-house with our Engineers and Level 3 Specialists. Many NDE projects have been developed to advance legacy inspection technologies with modern functionality. For example, it has been a long term continuing goal to transition from “Film” radiography into “Digital” radiography; standard ultrasonic shear wave inspection to advanced Phased Array Ultrasonic Inspection; standard eddy current inspection to advanced Eddy Current Array. Each of these transitions have taken place with initial feasibility studies, technique development, equipment development, determination of critical flaw sizes, flaw type, and inspection locations, technician training, qualification and final implementation.

SpaceX looks to the future for advances in newer inspection technologies as well. We have worked at developing Full Matrix Capture Ultrasonics as well as Laser Shearography and Thermal Imaging. In both cases whether furthering legacy inspection methods or transitioning into futuristic inspection methods, we follow fundamental engineering practices of technique development, qualification, validation, and in some cases Probability of Detection studies to verify (90/95) detectability.

The future of cost-effective access to space and our solar system is dependent of highly reusable advance spacecraft. NDE is an integral part in achieving that ultimate goal.

Counterfeit, deficient or non-conforming raw material entering the United States’ supply chain has become epidemic in recent years. Of specific concern is raw material used to fabricate critical components used as repair or replacement parts in existing systems in the country’s land and air-based weapons and defense systems. With the Department of Defense (DoD) working to keep our fleet, aircraft and weapons systems in top working order, it has become critical that parts and components be designed and manufactured from appropriate material. Replacement parts, components and assemblies made from substandard, non-conforming, fake or counterfeit raw material may lead to catastrophic failure; endangering personnel and adversely affecting homeland defense.
This problem is not exclusive to the DoD; private industries such as shipbuilding yards, aviation and aerospace manufacturers, organizations using additive manufacturing processes, automotive manufacturers, Department of Energy, Supply Chain Centers, etc., are wasting already constrained resources struggling with risks and failure rates caused by unacceptable material entering the supply chain undetected.
A team consisting of Ocean Bay, LLC, Savanah River National Laboratory and Old Dominion University formed to support Defense Logistics Agency (DLA) request for a single nondestructive device that could identify suspect material. Using the measurable properties of existing technology, and the physics of nondestructive testing methodologies a new inspection device, capable of field inspections for product/material compliance has been designed. This innovative NDT inspection process is intended to be used as part of a comprehensive inspection strategy to promote efficiency of use, design requirement verification and cost savings.

Combined NDT Correlation to Estimate the Compressive Strength of Concrete

This paper deals with estimating the compressive strength of concrete specimen using the combined method of ultrasonic pulse velocity (UPV) and rebound hammer (RH) tests. Compressive strength is an important parameter to evaluate concrete structures. Generally, the destructive methods like removing ‘core sample’ from an existing structures are considered as reliable methods to assess the quality of concrete already in place. However, these test methods are expensive and can be detrimental to the structure. Nondestructive tests like UPV and RH tests are used to overcome these disadvantages. They are widely used to assess the quality of concrete. The individual test results from UPV or RH methods may not be reliable for estimating the compressive strength, as there are different factors like aggregate size, curing age, and curing conditions that influences the measurements. In this study, several concrete samples were casted based on three different mix designs with the targeted compressive strengths of 41 MPa, 55 MPa, and 83 MPa. All of the concrete samples were cured under laboratory conditions and tested after 28 days curing period. UPV and RH tests were performed followed by crushing the cylindrical samples to evaluate the compressive strength. Effect of moisture on UPV and RH measurements was studied and the results have shown that RH measurements are significantly affected by the moisture in concrete specimens. The results from both UPV and RH tests were combined and correlated to the measured compressive strength values. This study was focused on creating a correlation curve by combining the results from UPV and RH tests and then performing multiple regression analysis between UPV, RH, and the measured compressive strengths. The accuracy of this correlation curves was determined by comparing the estimated compressive strengths to the measured compressive strengths.

Laser brazing offers several advantages over other high-volume joining techniques, most notably a lower thermal input compared to welding, helping avoid loss of strength of the substrate material and minimize part distortion. In the automotive industry, the quality of brazed joints is currently determined by visual inspection, followed by destructive cross sectioning, adding considerable cost to the production of some parts. Therefore, a non-destructive technique that allows for measurement of the internal joint geometry is highly desired.
To achieve robust, non-destructive inspection of brazed joints, development of an ultrasonic phased-array technique capable of compensating for the variable joint geometry that is typical in production was undertaken. Post-processing of ultrasonic full matrix data using the total focusing method, which allows for secondary corrections to be applied after an image is formed, was performed. By detecting the boundary present between a coupling agent and the braze surface, Fermat’s principle can be applied to determine the delay laws necessary for focusing through the boundary. Although this correction has been used with success for some brazed joints, issues were found when the high curvature of the joint upper surface resulted in a self-focusing effect. In these cases, amplitude corrections were needed in addition to phase corrections. A real-time implementable method for determining these amplitude corrections has been developed. The results of imaging using this additional correction will be presented, along with a comparison to the traditional technique.

Many researchers have investigated an oblique-incidence ultrasonic backscattering approach, often called polar backscatter [Bar-Cohen and Crane], which demonstrated measurement of local fiber directions in composites, but impractically required mechanical rotation of a transducer around each measurement point. The author proposes the hypothesis that scattering from the fibers spans an angular range broader than that subtended by a standard pulse-echo transducer, and that its angular distribution conveys the fiber orientations within the interrogated volume.
We built an array of 96 planar immersion transducers (0.25-inch diameter, 2.25 MHz) mounted on a spherical shell of radius 7 inches, in a hexagonal pattern with 3.6° minimum angular spacing, forming a cone of half angle just under 19°. Transmitting with one element and receiving with all elements in parallel, this arrangement provides angular sampling of the scattering from specimens.
Measurements were made on a quasi-isotropic, 8-ply laminate. We transmitted a short pulse from the element located at (polar, azimuthal) position (18.7°, 90°). The dominant surface reflection signal was received at (18.7°, 270°) and surrounding elements. When oriented perpendicular to the 0° fiber direction, the signal received at the transmitter (polar backscatter) was -22.8 dB compared with the baseline -39.9 dB. On either side, we observed signals at 12.98° from the normal, rising to -22.4 dB and -31.7 dB at angular locations of +103.9° and -101°, respectively, from the source direction. All these signals rotated in synch when the part was rotated, suggesting that the out-of-reflection-plane signals were scattered from the fibers at ±45°.

Ultrasonic 3D micro-characterisation of 2D and 3D-woven Composites

Presenting author(s):
Dr Robert A Smith

Co-Authors:

Room: Grand E-F Ballroom | 9:40 AM Tuesday, April 2, 2019

There is a growing cross-sector realization of the benefits from using complex 2D and 3D-woven composites for a broad range from high-performance aerospace components through to high-volume mass-produced automotive parts. This is accompanied by an increasing demand for improved non-destructive evaluation methods that can provide detailed information of the internal microstructure of these complicated weave patterns. This paper will report on the use of ultrasonic inversion methods, previously applied to unidirectional composites, for characterizing the more challenging woven composites. The basis of the inversion is the analytic signal and the instantaneous parameters of amplitude phase and frequency, which provide insight into the spacing of yarns and the thicknesses of resin layers at each 3D location in the structure. From this information, the weave can be classified and characterized, followed by comparison with the designed weave in order to detect deviations from design. Extending this to complex shapes where the woven composite is draped over a curved tool, allows mapping of rotations and distortions due to that draping process. Refinements to these methods and the development of new methods will be reported with reference to both modelled and experimental ultrasonic data on both 2D and 3D woven materials.

The expanded use of hydrogen power offers many benefits to the United States’ energy portfolio due to its versatility, low carbon footprint at the point of use, and high energy mass-density. However, the volatility of hydrogen coupled with deleterious interactions between hydrogen and storage mediums (e.g., hydrogen embrittlement) pose safety risks and limit widespread adoption. This project focuses on development of NDT techniques for enabling quality control of materials used in construction of hydrogen storage systems and for detecting early-stage damage in materials in contact with gaseous hydrogen during service. The approach leverages nonlinear acoustic wave mixing to enable sensitivity to micrometer-scale flaws that may reduce resistance to hydrogen embrittlement and serve as failure initiation sites.
Acoustic wave mixing approaches have shown promise for identifying micrometer scale damage features related to thermal degradation, plastic deformation, and microcracking. In this study, we explore various experimental configurations for characterizing micrometer-scale damage in steel alloys using wave mixing techniques. The goal of this work is to optimize the measurement approach for hydrogen infrastructure inspection and to down-select to the most suitable method for detecting of both the severity and orientation of damage features in relevant materials.
During the initial stages of this development effort, measurements were made on specimens of 4140 with seeded micrometer-scale damage developed through early-stage fatigue loading. Measurement results show significant, localized growth in material nonlinearity at the damage region and sensitivity to damage orientation with respect to the measurement hardware. These promising results may lead scanning capabilities for profiling damage size and shape for useful life estimates of hydrogen storage vessels in service.

Process Monitoring at Capacitor Discharge Welding

Presenting author(s):
Mr Joerg Zschetzsche

Co-Authors: Mr Uwe Fussel, Mr Max-Martin Ketzel

Room: Grand E-F Ballroom | 10:00 AM Tuesday, April 2, 2019

The quality of welds can be proven by non-destructive or destructive testing. According to the state of the art, these quality checks are expensive and lower the economy and productivity. Hence, only on a random sample with few components, compared to the amount of all manufactured components, are tested in intervals. However, process monitoring can be used with high economy and low cost for a continuous quality assessment of all components.

The example of resistive projection welding with capacitor discharge (CD-welding) shows how the process sequence is designed on the basis of a physically justified process understanding and how the monitoring parameters are selected.CD-welding belongs to the resistance welding methods in which the connection is made by pressing the components and simultaneously melting a projection. According to recent researches, the joint is formed differently at cd welding. Due to very high power density within very short period of time metal vaporizes and activates the surfaces. The joint occurs in less than a few milliseconds, when the activated surfaces are pressed together while the projection is plastically deformed. At the same time, molten material is pushed out of the joint plane.

On this new basis of process understanding, a new machine has been developed in order to control the process purposefully and to monitor the stages of the process.

Nonlinear resonant ultrasonic spectroscopy (NRUS) is a resonance-based technique that gives a measure of non-classical (hysteretic) nonlinearity by quantifying the resonance frequency shift with increasing driving amplitude. NRUS offers great potential for the Nondestructive Evaluation (NDE) community, as it is relatively simple to implement and sensitive to the presence of incipient damage. Previous research has shown that NRUS exhibits high sensitivity to distributed damage in a wide variety of materials. In this study, the feasibility of using NRUS to assess local progressive damage in metals is investigated. To that end, an aluminum sample is subjected to three-point bending fatigue test to initiate a single fatigue crack. The cyclic loading is interrupted at several stages in order to image the crack using Scanning Electron Microscopy (SEM) and to perform NRUS and other tests. As the crack grows and increases in length, NRUS shows a corresponding increase in the resonance frequency shift. However, the trend for the amplitude dependency of resonance frequency shift is different from what has been previously reported in materials with distributed damage; the rate of resonance frequency change is greater at low strain, then gradually decreases and becomes constant as strain increases. In addition, an automated impact is employed to establish the applicability of impact-based NRUS to distinguish between intact and fatigue cracked aluminum samples. Impact-based NRUS clearly differentiates the fatigue-damaged from the intact sample and shows a similar resonance frequency shift vs. strain relation as that observed in the conventional NRUS. These results highlight the great potential of NRUS in detecting local damage, although the micromechanical mechanisms behind the observed anomalous strain-dependency of resonance frequency shift needs to be further investigated.

Adhesively bonded joints are an excellent replacement of traditional mechanical joints in the automobile industry, which are lightweight and cost-effective in fabrication. Electromagnetic induction heating technique with reversible adhesive is gaining popularity, due to its site-specific heating and maximized productivity with reduced energy consumption. Further, reversible joints offers the flexibility to restore the bond properties when there is damage during its service life. However, induction bonding process is less reliable to conventional oven bonding techniques due to its non-uniform heating, lack of monitoring and controlling techniques. This research work focuses on developing a controlled Electromagnetic induction heating system along with guided wave sensors for real-time process monitoring. This closed loop system is developed by taking advantage of hysteresis- and conduction-based heat transfer within the adhesive layer. The proposed technique helps to avoid adhesive degradation due to overheating and kissing bonds due to partial heating. Bond properties and strength are validated with distributed optical sensors and mechanical tests. The control system added to electromagnetic induction heating technique demonstrate the potential to increase the confidence in implementing this technique for industrial applications.

Polymer based additive manufacturing (AM) process has recently gained attention in several industrial applications for building complex components and parts in automotive, oil and gas, aviation and aerospace. Poor interlayer adhesion of the printed components is the most common type of defects in the parts made by this process. These weak interfaces result in poor mechanical properties in the out of plane direction (i.e. perpendicular to the print plane) of the printed structure. Conventional ultrasound techniques are incapable of detecting and quantifying such defect. In conventional ultrasound testing techniques, the poor interlayer adhesion transmits most of the sound energy limiting the detection capabilities using either pulse echo or through transmission inspection modes. Nonlinear ultrasound techniques, however, have shown promising results in detecting similar defects such as fatigue cracks that exhibit the same limiting detection condition. Researchers investigate the behavior of nonlinear ultrasound in frequency domain which has shortcomings. In this research, behavior of nonlinear ultrasound technique in phase-space domain in the poor interlayer adhesion of printed layers is investigated. The initial experimental results on samples developed at Oak Ridge National Laboratory (ORNL) showed that this technique potentially can be used for the characterization of the interlayer adhesion in the parts built by the polymer based AM process.

Dr Roman Gr Maev

University of Windsor

Roman Gr. Maev Short Biography

Dr. Roman Gr. Maev is the founding Director-General of the Institute for Diagnostic Imaging Research - a multi-disciplinary, collaborative research and innovation consortium – and also a University Professor, Distinguished.

The extraordinarily diverse range of disciplines encompassed by Dr. Maev includes theoretical fundamentals of physical acoustics, research in ultrasonic and nonlinear acoustical imaging, nanostructural properties of advanced materials and its analysis. He has published over 592 peer-reviewed items, including 23 books and chapters in books, and 30 issued patents and has 17 patents pending(filed).

He is a recipient of many international awards. Dr. Maev is also, a Fellow of IEEE, a Fellow of the British Institute of NDT.

Ultrasonic Non-Destructive Evaluation for Real Time Regulation of Welding Schedule

Dr. Roman Gr. Maev is the founding Director-General of the Institute for Diagnostic Imaging Research - a multi-disciplinary, collaborative research and innovation consortium – and also a University Professor, Distinguished.

The extraordinarily diverse range of disciplines encompassed by Dr. Maev includes theoretical fundamentals of physical acoustics, research in ultrasonic and nonlinear acoustical imaging, nanostructural properties of advanced materials and its analysis. He has published over 592 peer-reviewed items, including 23 books and chapters in books, and 30 issued patents and has 17 patents pending(filed).

He is a recipient of many international awards. Dr. Maev is also, a Fellow of IEEE, a Fellow of the British Institute of NDT.

Co-Authors: Dr Andriy M Chertov, Mr Sunghoon Jung, Mr Sanghyun Yoo

Room: Grand E-F Ballroom | 10:40 AM Tuesday, April 2, 2019

Resistance spot welding technology is used in the sheet metal assembly industry to join two or more metal sheets. It is a completely automated and robotized process today. Modern weld controllers have the capability to adaptively deliver welding current based on the measurement of current, voltage and, sometimes, electrode force. Such an approach allows to better regulate the amount of heat developed in the welded area and to produce a good quality weld.
Due to some unavoidable tolerances in the metals such as coating or sheet thickness variation, shunting effects, complex part geometry, electrode tip wear, etc., in all such cases, measurement of the current and voltage is not enough to reliably deliver the needed amount of heat. Thus, there is potential to produce undersize or cold welds.
In recent years, Tessonics Inc. (Windsor, ON, Canada) has developed a patented ultrasonic system capable of monitoring the spot weld formation in real time. Melting of the base metal can be observed directly and this information can be used to feedback the welding controller. OBARA Korea was chosen as a strategical partner to develop the new generation of an adaptive system based on ultrasonic monitoring of the welding process. The project is running with financial support from both Canadian and Korean Government Funding Agencies.
This paper will illustrate the basic principles of the newly emerging technology.

Ultrasound sensors are frequently used to generate acoustic waves capable of detecting cracks, pits, erosion, inclusions, etc. One problem with piezoelectric transducers, particularly in harsh environment applications, is the difficulty to achieve coupling between the transducer and the structure. This work explores the behavior of a magnetostrictive (ms.) cold-spray patch on a stainless steel inspection target, and compares it to the performance of a standard adhesively bonded ferrous-cobalt ms. strip. Cold spray is a process where powdered metal is accelerated to 2–3  speed of sound and impacted on the surface forming a metallurgically bonded coating. If the powder is nickel or cobalt with high ms. coefficients, this surface can serve as the base of an SH-0 or A-0 Lamb wave mode EMAT sensor suitable for crack or pitting corrosion damage monitoring that is not subject to temporal or environmental degradation. Guided-wave ultrasound edge reflection signals from adhesively applied FeCo strips were compared to nickel or nickel alloy cold-spray coatings applied with various process parameters. The ms. coefficient of nickel is less than half of FeCo so some reduction in amplitude was expected. Cold-spray responses ranged from a moderate increase to > 40 dB reduction. The signal/noise ratios though were > 26 dB. Based on the edge reflection amplitudes and signal/noise, the inspection sensitivity is inferred to be manageable by instrument gain adjustments and, therefore, the cold-spray patch would be a viable alternative to an adhesive strip sensor that is not subject to coupling or adhesive degradation.

Dr. Fry will introduce and discuss a few of the grand challenge
areas in nondestructive evaluation (NDE) of railway infrastructure systems and
rail equipment. The common theme is that future NDE technology should be
automated and fully compatible with the emerging norms in predictive analytics
that the industry is developing. As a particular challenge, future
“full-section-rail” (FSR) and wheel/axle detection systems should be capable of
performing in-motion and reporting in real time.

Discussion for Testing of Rail Foot or Base and Need for Detection Methods

Presenting author(s):
Mr Ian S Weiner

Co-Authors:

Room: Grand E-F Ballroom | 2:00 PM Tuesday, April 2, 2019

Detection of transverse defects in the base area of the rail. This is a challenge for the railway industry due to these going non-detected and causing service outages or more catastrophic events. These are very challenging as they can fail at a very small size and can occur on any track.

Currently, there are no productive in-track dynamic methods to detect these flaws. There are more than 200,000 miles in the North American track networks. This is becoming one of the highest causes of derailments and broken rails. The failure causes range from welding procedures not followed, fatigue failures, corrosion causing pitting and anchor compression nicks.

This presentation will provide failure causes and conditions. This will cover the welding procedures that cause the failures, base fracture failure from rail seat abrasion or corrosion and current inspection methods

Mockup Evaluation of Omnidirectional Magnetostrictive Transucer

Presenting author(s):
Dr Sergey A Vinogradov

Co-Authors:

Room: Grand G Ballroom | 2:00 PM Tuesday, April 2, 2019

The use of guided waves for long-range inspection of components is a rapidly growing area of the nondestructive evaluation (NDE) service industry. Magnetostrictive sensors utilizing ferromagnetic materials are an effective transductor technology that has been available for several years for guided wave testing of a great variety of components. A major application area for these sensors is the inspection of plate-like structures given the comparatively large coverage area (up to 100 square meters) from a single transducer location. A novel omnidirectional scanner was developed recently using the magnetostrictive sensor technology for inspection of these structures. This scanner combines a single-direction plate wave transducer and a servomotor to rotate the transducer during a scan. The transducer design allows for operation at multiple frequencies and it is usable on plates with wall thicknesses up to 25 millimeters. The guided wave data that is received is either analyzed as B-scans or combined together using a synthetic aperture focusing technique.
The transducer design allows utilizing both shear horizontal and Lamb waves. From the stand point of practical NDE, one of another type of guided waves has advantages and limitations. During this research, data were acquired from a 12.5 mm wall carbon steel plate with 24 different anomalies representing wall loss from 15% to 100%. Both modes of guided waves in frequency ranges 70 to 120 kHz were used for data collection. Results of the test will be discussed in this presentation.

Rail integrity inspection has been traditionally performed through ultrasonic water-filled wheels, called Roller Search Units (RSU) in contact with the rail head. Although RSUs are effective in detecting most internal rail defects, inspection speeds, on average, are less than 30 mph due to various factors. The low speeds and need for separate inspection vehicles forces railroads to schedule track inspection windows that may disrupt regular train traffic.
The proposed rail inspection technique is unique in the following manner: (1) Passive Only – no active transducer excitation is needed, and transducer elements are used solely in detection, and (2) Non-Contact – ultrasonic elements for detection are situated above the rail head with air as the sole coupling medium. Instead of using an active transducer, acoustic excitations generated by the rolling train wheels are used as the “active source.” The ultrasonic elements detect the acoustic excitations and reconstruct a stable ultrasonic transfer function, independent of the randomness of the wheel excitation. The features from the reconstructed transfer function are used in an outlier detection algorithm to highlight the presence of rail defects or discontinuities.
Results from test performed at Transportation Technology Center (TTC) at Peublo, CO on the RTT (Railraod Test Track), RTDF (Railraod Track Defect Facility), and HTL (High Tonnage Loop) demonstrate the potential for the passive-only non-contact rail inspection. Once fully developed, this mode of inspection may open the door to perform rail inspection with little to no traffic interruption while having higher levels of rail safety from redundancy from multiple train passes along the same line.

Mr Pierre Belanger

Professor Pierre Belanger holds a PhD from the NDT research group of Imperial College London. He has been a professor in the department of mechanical engineering at ETS since 2013. His current research interest focuses on novel applications of ultrasonic bulk and guided waves as well as the development of innovative transducers. He collaborates with a range of companies from equipment manufacturers, to service providers and large OEM in the automotive and aerospace industries. He is currently the chairman of the Olympus Industrial Research Chair on Ultrasonic Nondestructive Testing.

Professor Pierre Belanger holds a PhD from the NDT research group of Imperial College London. He has been a professor in the department of mechanical engineering at ETS since 2013. His current research interest focuses on novel applications of ultrasonic bulk and guided waves as well as the development of innovative transducers. He collaborates with a range of companies from equipment manufacturers, to service providers and large OEM in the automotive and aerospace industries. He is currently the chairman of the Olympus Industrial Research Chair on Ultrasonic Nondestructive Testing.

Co-Authors:

Room: Grand G Ballroom | 2:20 PM Tuesday, April 2, 2019

Friction stir welding (FSW) is a solid state joining process used across a range of industries from shipbuilding to aerospace. However, defects such as kissing bonds or wormholes usually associated with poor control of the rotational and traverse speeds during manufacturing remain difficult to detect using standard nondestructive testing methods. This paper investigates the correlation between the transmission of low-frequency guided waves through a lap joint and weld properties. The aim of the method is therefore to nondestructively screen friction stir welded lap joints to assess the welding properties rather than detect specific defects. The experimental setup comprises a 100 kHz shear transducers used for the excitation of S0, six 3 mm aluminum plates friction stir welded in a lap joint configuration and a 2D laser vibrometer. The lap joints were manufactured at different tool rotational speeds between 600 RPM and 1050 RPM. The linear transmission of ultrasonic guided waves showed a remarkable agreement with the very important width of stir zone. When using nonlinear ultrasonic guided waves, a clear outlier at 750 RPM was identified and further investigation using weld cross-sectional analysis was performed.

In-Service Rail Inspection with Eddy Current

Presenting author(s):
Mr Eric A Eberius

Co-Authors: Mr Dietmar Griem

Room: Grand E-F Ballroom | 2:40 PM Tuesday, April 2, 2019

Detection of Rolling Contact Fatigue (RCF) on the surface of
railroad rails with eddy current is becoming more common in the maintenance and
service of transit lines and heavy haul rails. Use of eddy current information
to determine rail surface condition to aide with required corrective
maintenance and preventative maintenance are becoming viable strategies for
railroaders. Walking sticks and installed high rail systems are tools that are
used in this effort. This general overview includes recent efforts to detect
surface flaws located on railroad rails in North America with Rohmann’s
draisine; portable walking stick device. From R&D efforts in the lab and
on-track testing at designated test sites to in-service results, this
presentation shows the latest efforts from Rohmann with regards to detections
of rolling contact fatigue (RCF) and related surface conditions as well as the
impact of grinding train signatures on rails with RCF.

Global-Local Modeling of Guided-wave Scattering for Quantitative NDE

Presenting author(s):
Ms Margherita Capriotti

Co-Authors: Mr Antonino Spada, Dr Francesco Lanza di Scalea

Room: Grand G Ballroom | 2:40 PM Tuesday, April 2, 2019

Among the several NDE and SHM techniques, ultrasonic guided waves are very suitable for the inspection of wide structures and complex geometries. Their behavior and interaction with geometrical or potential defective discontinuities needs to be understood to assist the experimental set-up of NDE tests and to interpret the collected data for quantitative damage detection and structural characterization.
The Global-Local method is utilized here to investigate the guided-wave scattering in presence of very complex geometries, involving multi-layered materials and various types of defects. The standard Finite Element (FE) approach discretizes the region with discontinuities, while the Semi-Analytical Finite Element (SAFE) method discretizes the cross-section only of the waveguide geometry and propagates the solution along the wave propagation direction, analytically through eigenvector decomposition. The two problems are coupled at the interacting boundaries in terms of tractions and displacements, to guarantee energy conservation. The scattering coefficients due to an incident wave mode are calculated by least square method and will be used in terms of reflected and transmitted energy and cross-sectional Poynting vectors to understand frequency-mode sensitivity to defects.
Results will be shown for the skin-to-stringer assembly of composite aircraft structures that are affected by various types of impact damage that are relevant to aircraft safety.

UT and Ancillary inspections for Railroads

Presenting author(s):
Mr Max Lafferty

Co-Authors: Mr Troy L Elbert

Room: Grand E-F Ballroom | 3:00 PM Tuesday, April 2, 2019

There are many challenges to overcome to become proficient in the rail testing industry. One must be open to change and flexible to meet a dynamic demand from the market. Along with ultrasonic inspection for internal defects, opportunities arise for ancillary inspections to help the railroads determine the overall health of the rail. This paper will discuss the basics of ultrasonic rail testing, some of the challenges associated with ultrasonic inspection and ancillary tests such as Rolling Contact Fatigue, Geometry and LiDAR. Integrating these high volume and complex data sets into what the industry calls “Big Data” can be cumbersome and difficult to analyze using traditional statistical analysis techniques. Thus, important information to help modern railways plan their capital maintenance programs, there is a need for the applicable of new and improved analysis techniques to make this conversion from data into information.

A Novel Guided Wave Method for Detecting Gas Entrapment in Piping

Presenting author(s):
Mr Michael J Quarry

Co-Authors:

Room: Grand G Ballroom | 3:00 PM Tuesday, April 2, 2019

This study developed a novel method based on guided waves to detect the presence of gas accumulation in piping systems. Nuclear power plant systems have continued to be challenged from gas accumulation in both safety related and safety significant piping systems. Excessive gas voids in liquid bearing piping systems which feed pumps can cause severe pump damage and in a worst case scenario, they can cause the pump to air bind making the system inoperable. The presence of a vent valve may not be easily accessible and periodic venting may pose a risk to personal safety. This combined with the fact that venting of some valves leads to higher than wanted dose rates, presents the need for an online monitoring system. Issues include dose rates, inaccessibility, scaffolding expense, and insulation removal.
The method utilizes the guided wave response of certain modes and frequencies from features in a piping system, such as welds or symmetric attachments. Analyzing the guided wave response has shown a qualitative approach to detecting a gas void in a liquid filled pipe. Calculations using this approach show a method for estimating the size of the void were performed on an experimental mockup and compared to ultrasonic measurements of the void.

Resistance spot welding is currently the main process of joining metal sheets in automotive industry. Although there is multitude of ways to ensure proper current/heat delivery into the weld spot, still there is no acceptable solution for the robot to tell the quality of each produced weld joint in real time during the manufacturing process. After more than 35 years of successful application of robotic spot welding in the industry, the quality of welded joints is still determined by their post-process evaluation. All current means of ensuring the proper functioning of robotic spot welders are indirect and based either on measuring current, voltage, force and displacement, or selective post-welding inspection of the formed joints. Both approaches do not satisfy quality demands of the automotive parts assembling industry.
As an alternative solution, the Institute for Diagnostic Imaging research, University of Windsor (Windsor, Canada), has developed an ultrasonic spot weld monitoring system prototype for automatic real-time quality inspection of the formed spot welds. The Narmco Group (Windsor, Canada) expressed interest in customizing and testing the system prototype by installing it at Narmco PMS plant (in Gadsden, AL, USA). The goal of the project is to validate the system prototype at the assembling line. The project is funded by the Narmco Group and National Science and Research Council of Canada (NSERC).
The first implementation results of this advanced real-time nugget quality inspection technology are discussed in the offered paper.

Computer-based modeling of the phased-array transducer’s acoustic energy can help save time and money and significantly improve the end-result, when solving new or difficult UT exams. The paper will include a specific case study, including 3D simulations, for the examination of ½” dia. X ¾” long nuclear bolts. The example will cover the entire process from customer requirements to prototyping and field results.

The paper presents work in developing an inverse path planning system to read native CAD surface data and program accurate and collision-free scan paths for NDT. Any chosen inspection system needs to be accurate and fast thereby ruling out the use of manually operated scanning devices for the large parts. We focus our applications on aerospace and defense manufacturing of composite structures.
The use of robotic systems mounted on external axes for NDT can offer flexibility in terms of reach and accessibility. Programming the robots and ensuring collision free motion through the large number points is an impossible task using the conventional teach pendant programming methods. This paper will present a new approach developed for automatically programming NDT robots or Cartesian axis machines quickly and ensuring that the path is collision free and accurate.
A number of NDT methods including Ultrasonic and vision camera based techniques are available for inspecting or testing composite parts. Each method has specific benefits and disadvantages. Today Ultrasonic testing methods are becoming more popular since they are flexible and relatively easy to implement in a general production environment, the drawback however is that the method requires use of a medium to conduct sound and therefore becomes more cumbersome to implement in a production line inspection setting.
Robotic applications are growing quickly and the need for more automated programming solutions has become evident. The proposed method has been validated in numerous industrial applications, is highly interactive and requires minimum knowledge of robot programming and is extremely effective for programming complex NDT cells where multiple robots are used or cases of master slave robot operations for through skin inspection process where one robot is transmitting the signal and the other one is set to receive the signal. If a vision camera system is used for the inspection process then the off-line robot programming (OLP) system must account for the parametric constraints of the camera such as focal length and focal distance. Furthermore, the OLP system needs to be able to demonstrate visually all areas of the part which the camera is not able to inspect so that other methods of inspection can be applied if 100% part inspection is desired.
Several examples from customers in aerospace and nuclear industry will be presented with cases where the system is used to achieve the required programming efficiency and optimum cycle time.

This work addresses mode conversion and propagation in long pipes with non-axisymmetric circumferential and inclined angle cracks using finite element (FE) modeling and a hybrid simulation approach. First, the FE method was used to simulate guided wave scattering in a 12 inch diameter pipe and to study the effects of a crack’s geometrical parameters, such as depth, width, length and angle, on the propagating modes. A comb array transducer excited the first longitudinal mode at 120 kHz in the FE model and the simulations ran in parallel on a cluster computer. Dispersion curve calculations and the circumferential order identification approach were both implemented to identify newborn modes in the pipe as a result of defects. Each defect case is discussed in further detail. Additionally, a hybrid model, incorporating the FE method and an analytical solution, was introduced to find propagating modes at some distance along the pipe. This hybrid model uses a modal analysis-based analytical solution to find propagating signals at the intact sections of the pipe, while implementing a FE simulation for the cracked segment of the pipe. In essence, this hybrid approach dramatically reduces the time and computational power required to simulate high frequency wave scattering in long, defect-ridden pipes.

Automated Non-Destructive Evaluation of Spot Welds Using the Imaging Analyses of the Residual Magnetic Flux Density

Presenting author(s):
Mr Christian Mathiszik

Co-Authors: Mr Joerg Zschetzsche, Mr Uwe Fussel

Room: Grand E-F Ballroom | 4:20 PM Tuesday, April 2, 2019

Resistance spot welding is due to its high reliability and economy one of the most widely used welding methods in the automotive and railway industries. The high quality assurance requirements in these areas call for reliable non-destructive testing (NDT) methods of the spot welds. The weld or nugget is localized between the sheet metals and therefore not directly measurable from outside. This aspect continues to pose a major challenge for non-destructive quality assurance, especially due to the increasing diversity of used steel alloys in car body manufacturing.
At the Technische Universität Dresden, Germany, the imaging analyses of the residual magnetic flux density has been developed for NDT of spot welds. Up until now, the manual evaluation of the measurement results is time-consuming and subjective. In order to achieve greater reliability and to minimize evaluation times, an algorithm for automated evaluation has been developed. In order to evaluate the quality of the algorithm, the results are compared with NDT and destructive measurements of the same samples. For these samples, typical automotive steel combinations for spot welding were used.
This talk will show the measuring concept of the imaging analyses of the residual magnetic flux density for NDT of spot welds and presents the high potential of using an automated non-destructive evaluation algorithm for NDT of spot welds.

Acoustic Region of Influence for the Total Focusing Method (TFM) Beamformer

TFM imaging is a synthetic aperture focusing method which allows for inspection of a test specimen using multiple acoustic paths. The Acoustic Region of Influence (AROI), is the region in the TFM scan area where the flaws can be detected with sufficient SNR level. The AROI is affected by many factors, including among others, propagation media and flaw directionality. More importantly, the AROI is strongly dependent on the chosen inspection mode. Consequently, multiple inspection modes can be combined to obtain complete coverage of the scan area. In this paper, we will describe a wave propagation based theoretical model designed to calculate the predicted TFM AROI for both pulse-echo and self-tandem inspections. A methodology based on the usage of the developed model is proposed to plan and conduct TFM inspections with emphasis on weld inspection and weld bevel directional flaws. Experimental evidence is provided to support this approach, to assist inspectors in selecting or confirming the right mode selection.

Platform for Test Scripting and Automated Testing of Smart Meters

Presenting author(s):
Mr Vaibhav Garg

Co-Authors:

Room: Grand E-F Ballroom | 4:40 PM Tuesday, April 2, 2019

We have come up with a unique and tailor-made platform for the functional testing of Smart meters. This allows test staff with no programming experience to create highly complex test cases and test the Smart Meters autonomously.
Smart meters are one of the most vital cogs of Smart and connected Grid. Smart meters are essentially Internet connected smart devices, which communicate bi-directionally with a back end server, using a basket of technologies. Add to that the requirements for various combinations of electrical data, control, anomaly and fraud detection mechanisms and operating ranges, you are staring at very large test matrix corresponding to all the different combinations.
To add to the challenge above, Smart electric meters are designed and required to be non-serviceable, such that the integrity of the device in the field is undisputed and the data can not be repudiated. The devices are widely deployed, at every metering point; each home, office, factory, shop; each installation uniquely configured in some unique way.
Needless to say, the escapes to customer are both high impact and have high likelihood given the flux of change and that very large test matrix. The embedded and application software is designed to be resilient, reliable and must maintain data integrity in all conceivable field scenarios. Any changes late in the project life cycle introduce a huge risk of regression and project cost overruns due to regression testing.
Our platform allows the test staff to create test scripts. We decided that the most intuitive way of slicing the elephant with regards to module design would be to centre the task modules around interfaces to the Smart Meter. The Interfaces to a Smart meter can be either be electrical (Voltages, currents, frequency, power factors, wave shapes et. el.) or logical (Reading a certain value, writing a certain value), or User interface related (Smart meter Display- interpreted using a state-of-the-art Convolutional Neural Network, buttons et. el.). We abstracted these interfaces out and developed modules exercising each of these interfaces. Additionally, we added some modules for imperative programming constructs such as variables and constants, delay, looping, computations, file I/O and others. The connecting glue to all this is a sequencer, which can be used to put these building blocks in any sequence to run. Essentially, the test script creator drags and drops the relevant module in the script, configures the module using a GUI, and saves the test script. The saved script can be run at any point of time in the future. The test script creates a detailed audit trail to facilitate debugging if and when defects are found.
The test platform enables us to run the decided tests 24/7 alleviating the pain of regression testing. Another benefit that we have reaped is that the motivation for test staff has gone up, as a lot of grunt work can be offloaded to the machine.

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The numerical computation of eddy current pulsed thermography (ECPT) is an electromagnetic-thermal coupling problem. The excitation signal of ECPT is a small period of high-frequency current which increases the difficulty of simulation of ECPT signals efficiently and accurately in the time domain. The numerical method proposed in this study calculates ECPT signals efficiently in the frequency domain and the time domain. The numerical process of ECPT signals could be divided into two parts, the simulation of electromagnetic fields in the frequency domain and the calculation of temperature fields in the time domain. For the thermal analysis, as the heating period is very short, the heat transfer by convection and radiation is neglected. The air model is no longer needed either in the thermal analysis due to the heat conduction is the main type of heat transfer or in the electromagnetic field analysis as a result of the employment of the BEM makes it possible to avoid burdensome mesh generation work in air region. The excitation currents of electromagnetic fields could be decomposed into a series of sine waves of different frequencies according to the Fourier series method. The electromagnetic response signals, i.e., the thermal source of temperature fields, could be solved by first calculating the response signals of multiple single-frequency sinusoidal excitation currents using FEM-BEM method and then superimposing them. The thermal source is transformed to an equivalent simple form according to the energy equivalent principle due to the high frequency of the original thermal source. The temperature distribution signals of ECPT can be calculated through the time step iteration in the time domain.

The potential benefits of additive manufacturing (AM) technologies as part of the digital thread in advanced manufacturing are well established. These benefits have fueled an explosive growth in AM as a primary manufacturing tool, not only for prototypes. The widespread adoption of AM has forced the space industry to examine the impact of these technologies on mission assurance requirements for high reliability applications (launch vehicles, spacecraft). While the potential benefits are intriguing (cost, efficiency, performance), this is a technology in flux, with new participants, industry consolidation, and extensive hype in the popular literature. This presentation will outline work done at The Aerospace Corporation to examine the relevant physics related to specific AM processes (metallic and polymer), development of best practices in the industry and highlight ongoing inspection and quality assurance challenges in the Aerospace industry.

M-Wave is an emerging imaging technology that uses a resonating coil to generate an oscillating magnetic field which is transmitted into a test specimen and a resonating receive coil to intercept the field as it exits the specimen. Both coils are specially designed to resonate in a manner that greatly amplifies the fields ability to detect most types of material phenomena. M-wave is named after the characteristic ‘M’ shape of the frequency response curve it generates when both coils resonate ideally.
This ‘M’ shape creates a phenomenon previously un-utilized where the oscillating magnetic field becomes sensitive to glass, ceramic, metals, composites, conductors and non-conductors alike. It also has the unique ability to image through LO (Low Observable) coatings through to the composite substructure below. It can image through multiple walls of various materials separated by air gaps or other materials. It can image at standoff distances of up to 0.500” with several feet possible. The sensor is capable of imaging phenomena as small as 0.010” as well as cracks in metal, delamination in composite both cured and un-cured, primer and paint thickness and thicknesses of nonconductive material on substrates of material which are also non-conductive. It can detect differences in strong and weak adhesive bonds of various sorts including kissing bond in composite.
M-Wave is currently being commercialized and is in preliminary tests at Lockheed, Boeing, Northrop and various research labs.

Radio-frequency (RF) absorbing materials (RAM) are widely used to reduce electromagnetic interference and scattering from reflective (i.e., conductive) surfaces such as those utilized in aerospace and military applications. In particular for aerospace and military applications, structures of interest are often constructed of multiple layers of carbon-fiber reinforced polymer (CFRP) laminates. These structures can sustain impact damage (causing delaminations in the CFRP) that may not be readily visible through the RAM coating. Thus, it is important to nondestructively assess such structures for their structural health (i.e., defect detection). To this end, active microwave thermography (AMT) is considered as a viable solution. AMT is based on microwave and thermographic nondestructive testing (NDT) principles and utilizes a microwave-based thermal excitation. The resulting surface thermal profile of the structure or material under inspection is measured with a thermal camera. Defects present in the structure may affect the heat diffusion and present as indications in the resulting thermal image. As it relates to CFRP structures with a RF/microwave absorbing surface (such as radar absorbing material, or RAM), when RAMs are illuminated by microwave energy, this energy is absorbed. Therefore, the RAM can serve as a thermographic heat source to the underlying structure. In this way, subsurface defects can be detected and evaluated. The utility of this approach has been demonstrated in [1], where a thin RAM was placed on the surface of a layered structure containing a CFRP laminate placed atop a cement-based substructure. A delamination was present at the interface of the CFRP laminate and substructure. It has been shown that the presence of the defect was easily detected when the RAM was present. This work will extend this proof-of-concept work by investigating the potential for AMT to inspect for the presence of damage and delaminations in thick CFRP structures. The effect of RAM thickness, thickness of the CFRP structure, microwave frequency, and illumination angle will be investigated, along with delamination location and dimensions.
This work has been partially supported by the National Science Foundation Electrical, Communication, and Cyber Systems (ECCS) Award 1609470, “A Multi-Physics-Based Approach to Active Microwave Thermography”.
References:
[1] Mirala, A., M.T. Ghasr, and K.M. Donnell, “Nondestructive Assessment of Microwave Absorbing Structures via Active Microwave Thermography”, in Proceedings of 2018 IEEE International Instrumentation and Measurement Technology Conference, Houston, TX, May 2018.

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We live in the world of “aging infrastructures”. In this environment, critical and heavily-utilized infrastructure, such as ships, planes, bridges, etc., are operating at or beyond their designed life span. Replacement is no longer an option and “retirement for cause” is the current approach to maintenance and replacement. Consequently, there is an ever-increasing demand for efficient and robust nondestructive testing (NDT) methods that can determine the physical health of these structures. Large structures, which are primarily made of metals, are susceptible to high-stress cracking and corrosion. Every NDT method has its own limitations that in different ways limit its application for this purpose. Signals at millimeter wave frequencies (30 GHz-300 GHz) readily penetrate through dielectric materials such as paint and corrosion byproducts (i.e., rust), while conducting materials (i.e., metals) strongly reflect microwave signals. Therefore, interrogating a metal surface for surface-breaking cracks is readily possible even in the presence of a relatively thick layer of corrosion or paint. Similar to RADAR imaging, millimeter wave imaging can also take advantage of synthetic aperture radar (SAR) approach, which allows for many measurements from different locations and at many different frequencies to be coherently combined into a single image with much higher signal-to-noise ratio than a single-view or single-frequency image. This paper illustrates the capability of a wideband millimeter wave SAR imaging system to detect surface breaking cracks in heavily corroded steel and aluminum plates. The efficacy of the technique and its limitations will be discussed as well.

Structural health monitoring (SHM) is important to many industries including transportation, infrastructure, and aerospace, amongst others. As such, the measurement of structural parameters such as in-plane (or normal) strain, particularly two-dimensional (2D) in-plane strain, can be used to ascertain structural health. Currently, the options for 2D in-plane strain sensing are limited to optical fiber-based or ultrasonic strain imaging for medical applications (i.e. echocardiography). These sensing solutions are also limited to strain measurement in the local vicinity of the sensor (which can be prohibitive as it relates to SHM). As a result, this work proposes a 2D in-plane strain sensor that is realized using frequency selective surfaces (FSSs). Generally speaking, an FSS is a periodic array of conductive elements located on a dielectric substrate. The specific reflection/transmission response of the FSS, when illuminated with electromagnetic energy, is related to the element geometry, spacing and substrate properties. These features, in addition to their planar structure, ease of implementation, and wireless (remote) interrogation, make FSS-based sensors uniquely well-suited to SHM applications. In particular, parameters such as normal and shear strain, temperature, presence of defects/damage in layered structures, etc., may be monitored via FSS-based sensing. Moreover, as FSS sensors are planar, large areas may be monitored, with the inspection resolution adjusted from large- to small-scale based on the interrogation scheme. In this way, a coarse or fine strain profile (for example) over the monitored area (i.e., the sensor dimensions) may be determined from the measured frequency response. The proposed 2D strain sensor features a dual polarized slot-based dipole design and is capable of sensing strain in two in-plane directions independently by interrogating the sensor with an electromagnetic source with polarization (i.e., electric field direction) perpendicular to the direection of strain measurement. In addition, measurement of small-scale strain (i.e. on the order of 2%) is not affected by the presence of (additional) shear strain. However, larger values of shear strain (i.e., on the order of 4% or greater) will cause significant geometrical deformation in the sensor structure, thereby affecting the resonant frequency response of the sensor when under normal strain. To this end, this work will present representative simulations, highlighting the capability of the sensor to measure 2D in-plane strain. Also, as the presence of (additional) in-plane shear strain does have an effect on the sensor performance, this effect will be quantified through the corresponding error in the normal strain measurement.

Chipless RFID is a relatively new technology with a wide variety of potential applications, especially in the field of structural health monitoring (SHM). There is great interest in inkjet-printing chipless RFID tags, which are a type of wireless passive sensor, due to the cost savings and additive nature of this manufacturing method. However, when used at microwave frequencies there are some drawbacks in using this method of creating tags due to the limited conductivity associated with the tags as well as issues related to their durability. These limitations are of especial concern when it comes to possibility of using printed chipless RFID tags for structural health monitoring applications. In this study, a commercial inkjet printer was used to deposit silver nano-particle ink on three different papers commonly used for inkjet-printed electronics. Subsequently, their conductivity was measured using a microwave resonant cavity, operating in the frequency range of 8.2 – 12.4 GHz, and over time. The results showed significant variation in the measured conductivity of printed papers. In addition, that conductivity decreased over time as a result of handling (i.e., smearing and bending) of the prints. Furthermore, printing on different papers yielded different conductivities. These results were then coupled to surface roughness and print thickness measurements to provide a useful insight into the potential performance of these printed tags and their suitability for SHM applications.

Microwave induced thermoacoustic imaging (TAI) is a hybrid imaging technique that combines
electromagnetic radiation and sound waves to achieve high image contrast and superior spatial resolution. The method uses electromagnetic excitation to generate pressure waves in the imaged object via thermal expansion. TAI images have high contrast that reflects the variations of electromagnetic waves absorption in the imaged object, and high spatial resolution due to the short wavelength of ultrasound waves. These characteristics make TAI a good candidate to detect material anomalies that only change the material electric properties without a noticeable variation in material density. Regular TAI systems work by sending a single short pulse to the imaged target and then listen incoherently to the generated pressure signal; therefore, a very high-power (>10kW) pulse is needed to acquire images with high signal to noise ratio (SNR). Recently, the use of frequency modulated continuous excitation sources highly improved the SNR of TAI systems by using coherent detection with matched filters. The drawback of this approach is that it requires linear high-power amplifiers; therefore, it is not compatible with the current pulsed systems that are using vacuum tubes or spark gaps. This paper proposes the use of pulse width modulation associated with matched filters to enhance the SNR of the current pulsed systems. In this approach, a predefined pulse width modulated signal is sent to the imaged sample and then the received pressure signal is correlated with the derivative of the power of the excited signal. The proposed method highly enhances the received signal SNR and lead to a reduction in the required electromagnetic excitation power. The proposed approach can also be easily applied to the current pulsed systems and eliminates the need for the linear radio frequency amplifiers.

Over the past decades, composite materials and structures have attracted increasing attention and been widely used in a broad range of applications due to their unique properties such as high design flexibility, lower material cost, and increased productivity. Particularly, the lightweight feature and strong mechanical properties enable their potentials to fully or partially replace metal parts in a variety of applications. However, possible defects or damage such as disbonds, voids, or delaminations may significantly affect the strength of these materials. Nondestructive evaluation (NDE) techniques are highly desired to detect the presence of such defects to ensure the quality and performance of composite materials [1]. Many near-field microwave sensors and imaging methods have been proposed due to their high resolution and sensitivity towards dielectric materials. Among them, split-ring resonator (SRR) has been recognized as a useful tool for damage detection in composites, which behaves as sub-wavelength resonant tank structures [2]. These structures are able to constrain ssignal propagation in a narrow band, close to their resonant frequency, which can be potentially utilized for near-field and high-resolution sensing applications. A planar microstrip line coupled SRR sensor was designed in the GHz ranges and has been able to image surface or subsurface defects in composites [3]. These sensors are able to provide desirable diagnostic capabilities for a wide range of applications. However, there are some inherent limitations in this sensor design. For example, the size and planar geometry of the sensor limits the system’s ability to test large or complex-shaped samples. Additionally, some samples would require the scanning system to have a higher degree of mechanical flexibility. To address these problems, a flexible PCB-based SRR sensor is presented in this paper. The new sensor has the capability to conform to complex shaped geometries. The design can be optimized based on the desired degree of flexibility, scanning speed and imaging resolution. The experimental setup is designed with the assistance of an electromagnetic model built in ANSYS HFSS to get a better physical understanding of flexible substrate-based sensors. The developed SRR sensors provide good flexibility and spatial resolution with preliminary results demonstrating its capability as a promising NDE tool for inspection of composites.
References
1.R. Kline, Nondestructive characterization of composite media. Routledge, 2017.
2.J.B. Pendry, A.J. Holden, D.J. Robbins, and W. Stewart, “Magnetism from conductors and enhanced nonlinear phenomena,”IEEE transactions on microwave theory and techniques,vol. 47,no.11,1999.
3.S. Mukherjee, X. Shi, L. Udpa, S. Udpa, Y. Deng and P. Chahal,"Design of a Split-Ring Resonator Sensor for Near-Field Microwave Imaging,"IEEE Sensors Journal, vol. 18, no. 17,2018.
This work is supported by the National Science Foundation-Award No.:1762331.

Due to internal and external corrosions of the steel pipes, inner diameter (ID) and outer diameter (OD) surface defects occur every year, resulting in severe economic losses or even casualties. In the past two decades, to improve the transmission efficiency, the transmission speed and pressure inside the pipe have gradually increased, resulting in the inspection speed up to 8 m/s and the pipe wall thickness up to 15 mm. Thus, high-speed inspection of inner diameter (ID) and outer diameter (OD) surface defects on thick-wall steel pipes is an important aspect to advance the pipeline inline inspection (ILI) in the oil and gas industry. The state-of-the-art electromagnetic inspection methods are hardly applicable to practical high-speed pipeline ILI due to the reasons of the strong noise and low sensitivity caused by motion and the long time required for inspection. New inspection methods that offer faster inspection speed, better detection sensitivity as well as capability of ID/OD discrimination are imperatively needed. A novel fusion inspection method based on magnetic flux leakage and pulsed eddy current is proposed to detect and discriminate ID and OD defects for high-speed pipeline ILI. The fusion inspection probe including two-channel three-axis Hall-effect sensors and one-channel PEC coils are developed here. A novel 12" pipeline inspection gauge (PIG) designed and developed by the authors’ research group of Tsinghua University are used for field testing to validate the effectiveness of the proposed fusion inspection method that achieved high inspection speed, high sensitivity, low power consumption, easy implementation and ID/OD discrimination.

The detection of cracks in metals is a very important issue in civil and aerospace applications, and there is an ever-increasing demand for efficient and robust nondestructive testing (NDT) techniques capable of detecting these defects. Although many NDT techniques exist for this purpose, microwave and millimeter wave techniques have shown advantages compared to other techniques, including the ability to detect cracks through covering dielectric layers (such as paint or rust), and the ability to perform inspection from very large lift-off distances. The microwave and millimeter wave inspection techniques in use today involve the use of a linearly-polarized waveguide antenna or an open-ended coaxial antenna scanned (mechanically or electronically) over the structure and processed into an image, possibly using synthetic aperture radar (SAR) techniques. However, for linearly-polarized antennas, the probability of detection is dependent upon the orientation of the crack relative to the orientation of the polarization, and thus suffers from the risk of not detecting cracks if they are not oriented correctly. To ensure detection of all cracks, dual-polarized imaging (two different polarization orientations) must be utilized, requiring a two channel measurement system as well as either two separate antennas or a dual-polarized antenna. The open-ended coaxial probe does not depend on polarization orientation, but it can only be used for near-field (very small lift-off) imaging. A radially-polarized antenna allows the creation of dual-polarized images using only one antenna and without requiring a two channel (dual-polarization) measurement system. It can also be used for both near-field (small lift-off) imaging and the far-field (large lift-off) wideband SAR imaging. This presentation shows the utility of a radially-polarized antenna for detecting cracks on metallic surfaces regardless of orientation. Simulation and measurement results on metallic surfaces with surface breaking cracks are also presented.

Due to skin effect, conventional PECT can not detect defects in ferromagnetic materials in thick wall structure. However, by applying a saturated external magnetic field to reduce the permeability of ferromagnetic materials, it can effectively improve the depth of eddy current penetration and enhance the capability of PECT. To investigate the validity of the magnetic saturated pulsed eddy current testing method for detecting outer defect in thick structure of ferromagnetic material, the mechanism of magnetic saturation for increasing skin depth was explored numerically at first. Secondly, numerical simulations of pulsed eddy current testing signals under different magnetic permeability were performed for outer local wall thinning defects of different size, and the results are compared to clarify the effect of magnetic permeability. Finally, a pulsed eddy current testing system with magnetic saturation was established and the effectiveness of the magnetic saturated PECT method was proved experimentally. In addition, by making experiment with saturation magnetic field of different direction, it was found that the direction of the saturation magnetic field plays an important role to enhance the detectability of the magnetic saturated PECT method. The details will be discussed on the conference site. This work is supported by National Key R&D Program of China (2017YFF0209703) and NSFC (51877163).

Microwave and millimeter wave three-dimensional (3D) imaging has shown potential and utility for a variety of inspecting needs, such as for infrastructure and aerospace applications. Multilayered composites made of dielectric (non-conductive) materials, in particular, are prevalent in many industries and are often backed by conductive substrates made of metals or carbon composites. Millimeter waves, with frequencies in the range of 30 – 300 GHz, in particular are well-suited for nondestructive inspection of non-conductive composites where the relatively short wavelength allows high resolution 3D imaging while providing for signal penetration inside multilayered structures. However, the effect of a conductive-backing substrate on the 3D image, especially for targets near the substrate, has not been comprehensively studied. Multiple reflections and multiple signal paths encountered by the signal as it travels from the interrogating antenna to a targeted flaw, in the presence of strongly reflecting backing material, can make the 3D images highly susceptible to aliasing and distortion. Multiple targets can easily be mistaken for a singular, merged target indication, especially when they are in proximity to the strongly reflecting substrate. However, by properly accounting for the standoff distance of the antenna to the multilayered structure, the scan dimensions (i.e., size of synthetic aperture), and the distance from the target to the substrate, distortions in the target indications can be reduced and more accurate 3D SAR images can be formed. This presentation introduces a study using simulated and measurement results of the effect of the reflecting substrate on the formed images and techniques to reduce geometry dependent aliasing. This study is performed on multiple samples with a wide variety of target sizes, target proximity (laterally and vertically) to each other, and the polarization dependency of targets scattering (i.e., target shape).

New Approach for Detection and Characterisation of Micro-defects on Steel Spring Wires by Eddy Current Testing in High Speed Production Line

Presenting author(s):
Mr Mirmajid Ghaemi

Co-Authors:

Room: Grand G Ballroom | 10:40 AM Wednesday, April 3, 2019

Steel Spring Wires are small diameter wires ( mainly 40-150 mm ) that are used to make Spiral Springs for different applications in industries or vehicles specifically in cars . These wires are made usually by cold or hot drawing of large diameter bars and the subsequent rolling and finishing process like heat treatment and coating . At the end of production line the wires are wound in coils with total length of about 2 to 3 km . The production speed is usually between 30 to 50 m/min. The wires are primarily subject to torsional stresses such as in compression and extension springs and in special cases also for applications such as lever springs where the spring wire is subject to bending stresses . According to the worldwide common standard EN 10270, spring wires are classified in 3 grades : Static (FD), Medium Fatigue(TD) and High Fatigue(VD) grades. FD wire is characterised by its chemical , mechanical and technological characteristics as well as by a specified surface condition concerning surface defects and decarburization . But TD and VD grades are characterised additionally by high steel cleanliness and a well defined surface condition in relation to the allowable depth of surface defects and decarburization . The permissible depth of defects according to EN 10270-2 is between 0.005d to 0.015d depending on diameter d and the application . So far detection of major surface defects by a common Eddy Current Testing was a common practice but detecting and specifying the depth of minor micro defects was a difficult application and a challenging practice. Recently by developing modern and computerised Eddy Current testing instruments and very sensitive test coils a new approach is done to detect such micro defects .
In this paper the results of experimental trials on a hot rolled and tempered alloy steel spring wire with 10 mm diameter is reported . Tests has been done directly on production line with the sped of 30 m/min after hot rolling and hardening before coiling . Experiments indicated that the defects with minimum depth of 100 micron could be detected by a Differential Encircling Test Coil with Magnetic Saturation but for detecting defects with smaller depth the high speed Rotating Test Head equipped a sensitive differential probes are needed .

This presentation will offer insight into the structure of
the Chattanooga State Community College SACS and ABET accredited A.A.S.
Engineering Technology Degree in Nondestructive Testing and proposals on how to
balance laboratory time, OJT and internships.

Hydrogen induced cracking (HIC) has been a persistent issue in welding of high-strength steels. Fabricating HIC-free welded structures of high-strength steels, particularly the ultra-high strength martensitic grade steels can be difficult in field fabrication and repair. As a result, it is critical to control HIC. Four factors contribute to the HIC: susceptible microstructure, residual stress, hydrogen content and near ambient temperature. The current study develops a proactive in-process weld residual stress mitigation technique, which manipulates the thermal expansion and contraction sequence in the weldments during welding process. When the steel weld is cooled after welding, martensitic transformation will occur at a temperature below 400 °C. Volume expansion in the weld due to the martensitic transformation will reduce tensile stresses in the weld and heat affect zone and in some cases produce compressive residual stress in the weld. Based on this concept, customized filler wire with martensite phase transformation during cooling was developed. Y-Groove testing showed new filler wire showed significant improvement in terms of reducing the tendency of HIC in high strength steels. Neutron diffraction residual stress measurement revealed reduced tensile and compressive residual stress in welds made by new filler wires for the Y-Groove testing. Current, neutron diffraction residual stress measurement work of through thickness stress state in a multiple pass, restrained joint configuration, high-strength steel weldment will be presented. In addition, mechanical properties of new filler wire will be presented.

NDE at Penn State ESM

Presenting author(s):
Dr Bernhard R Tittmann

Co-Authors:

Room: Grand G Ballroom | 2:00 PM Wednesday, April 3, 2019

This presentation is focused on instruction of Nondestructive Evaluation NDE at the Department of Engineering Science and Mechanics (ESM)at the University Park Campus of the Penn State University. The presentation provides a list and description of courses related to Nondestructive Evaluation in the past few years. The courses were taught mainly by three Professors, Joseph Rose, Clifford Lissenden and Bernhard Tittmann on a year-around basis. The course program started with an upper division survey of NDE methods and then continued with several graduate courses specializing in various thrusts, such as Guided Waves, Ultrasonic NDE of Flaws, Survey of Microscopies etc. Each of the courses contained a design element in terms of student projects, reports and Power Point presentations. Student interest was high, especially in the upper division undergraduate course on Survey of NDE methods. Seniors from many different departments ranging from Mechanical, Architectural, Civil and Nuclear departments were regulars in this class. It may be concluded that NDE is perceived as an important element for any engineering position in today’s technology world.

GRCop-84, a copper alloy developed by NASA Glenn Research Center with the starting At% Cu-8 Cr-4 Nb, has a copper matrix with a fine intermetallic dispersion of Cr2Nb (cubic Laves phase C15). The alloy is being developed for high-heat-flux applications and has exceptional high temperature properties including retention of tensile strength at high temperatures, high thermal conductivity, and excellent creep resistance. The precipitated Cr2Nb have particles have limited solubility, strengthen the matrix, and reduce coarsening and diffusion effects which assists in thermal stabilization. GRCop-84 has empirically higher survivability rates than other metal additive alloys, good surface finish, and requires less operator tweaking for builds, and this is not fully understood. Neutron diffraction provides an accurate, non-destructive method of directly measuring the thermal stresses accumulated during production, which is also the primary source of failure before annealing. GRCop-84 has good scattering properties as it is mostly copper and the secondary phase can be characterized without excessive count times. The unstressed lattice spacing (d0), residual stress, and distribution have been characterized for simple shapes in HIP and as-built conditions made with SLM, a powder bed fusion method to provide missing information for future neutron studies. The HIPed samples show significantly reduced stresses concentrations than the as-built with a bias towards reducing compressive strain. And in-situ mechanical compression and tension tested have been conducted in a neutron beam to determine loading characteristics of annealed and as-built conditions and measure an accurate elastic modulus for the strain measurements. Neutron data was collected on ORNL's HB2B and VULCAN at HFIR and SNS.

SME Profile for Structural Integrity Design Teams

Presenting author(s):
Dr John C Duke, Jr

Co-Authors:

Room: Grand G Ballroom | 2:20 PM Wednesday, April 3, 2019

Nondestructive testing plays an important role in a wide range of applications from quality assurance to supporting assessment of fitness for service. For structures where structural integrity is essential the role of Nondestructive Evaluation is critical. The technical planning and design of such structures is typically carried out by a team of engineers spanning the necessary areas of subject matter expertise. The details of the aspects appropriate to the essential NDE engineering subject matter expert will be discussed. In addition, the educational background necessary for such a NDE Engineering SME will be identified; such a background although desirable is not required for a multi-method Level III inspector.

Dissimilar joining of materials is becoming more commonplace in modern, complex engineering components and structures. Along with this increase in complexity comes need for greater understanding of the composite mechanical and microstructural response of these joints. Neutron diffraction has become a more common technique for the non-destructive mapping of residual stresses in welds. To perform neutron diffraction measurements of dissimilar joints is more complicated than in a traditional similar weld. The staff at the strain-scanning diffractometer located at the High Flux Isotope Reactor (HFIR) at Oak Ridge National Lab (ORNL) have become world leaders in the practice of mapping residual stress in dissimilar joints. Results from both traditional welding, and dissimilar additive manufacturing samples are presented showing the effects of these sharp changes in material composition contribute to the residual stress profiles. Furthermore, the strain scanning diffractometer has recently been upgraded allowing for better measurement of dissimilar joints, these upgraded capabilities will be discussed.

Profile of Subsea NDE Engineer

Presenting author(s):
Mr Josh de Monbrun

Co-Authors:

Room: Grand G Ballroom | 2:40 PM Wednesday, April 3, 2019

This presentation will describe the types of applications and situations encountered in SubSea NDE. It will then describe the background technical education necessary to perform the job of an NDE Engineer in this industry sector.

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In
today’s industrial world, bearings are used in traditional applications such as
automotive, steel mills, paper mills, railways as well as high precision
applications such as aerospace, medical, renewable energy etc. Regardless of
application, residual stresses play an important role in the service life of a
bearing. In general, bearings experience Hertzian stresses in the order of 2-3 GPa
with maximum stresses generated in the subsurface. Depending upon the magnitude
and nature (tensile or compressive), the residual stresses enhance or reduce
the application stresses. The residual stresses are generated during each stage
of manufacturing process. For bearing components, the manufacturing stages
include – tube rolling, green machining followed by heat treatment and final
finishing. Majority of bearings are finished using abrasive grinding to achieve
the final size and shape. The work holding and material removal during the grinding
process can cause significant distortion. Distortion of bearing components is a
significant issue, especially for thin sectioned components, leading to high
scrap rates. In this study, neutron diffraction was utilized to understand the
evolution of through thickness residual stresses after abrasive grinding on a
thin walled bearing component. The results from neutron diffraction were
coupled with distortion measurements especially the out of roundness to
understand the effect of the final processing on the residual stress state
present in the bearings.

Professional Development Pathway for NDE Technicians and Engineers

Presenting author(s):
Dr John C Duke, Jr

Co-Authors: Dr Shant Kenderian

Room: Grand G Ballroom | 3:00 PM Wednesday, April 3, 2019

For many years a focus of ASNT has been on developing
a detailed process for training and certifying NDT technicians, Level I, II,
III. Much of the training is employer
based and focuses on the specific needs of the employer.

Recently the NDT
Engineering Education Committee was formed under the T&E Council
Engineering Division, and now part of the new Engineering Council.
This committee has been exploring the nature of the educational background
needed for both Engineers and Engineering Technologists working in the NDT
field. In that for educational programs a major concern is continuing
professional development this issue too has become a focus for the NDT
Engineering Education Committee because it may be a need that ASNT can
meet.

This issue will be discussed during the NDT Engineering
Education Committee prior to the presentation. A report of these discussions
will be provided and comments from those attending the presentation will be
welcomed.

This paper develops a method of determining pore characteristics and reports on the local distribution and intensities of pore orientations in the region of failure. A comparison of pore volume to the rest of the coupon volume will be presented. Test coupons produced by an EOS M290 additive manufacturing machine are used for the analysis in this study. The orientation of the principal axes of pore length with respect to the tensile loading direction are evaluated and analyzed for their effect on the failure of tensile coupons. Data collected from x-ray computed tomography (XCT) and reconstructed with VGStudio Max v3.1 produce three dimensional arrays of gray-scale data representing the test as-built geometry of the test coupons before tensile loading. Through a combination of deformable surface and global thresholding algorithms the pore geometry is realized. The developed method is disclosed and the distribution of the results is analyzed for the predicted effect on part failure. The results show that with both the local unification and the intensity of the sparse vector field, a fair prediction of the failure region in small tensile coupons can be made. Results are then compared with SEM images of the fracture surfaces and correlations are drawn. Further the validity of this predictor with scaling of the tensile test coupon is discussed.

MWM-Array and MR-MWM-Array Eddy Current Testing for Piping and Vessels

The MWM-Array and MR-MWM-Array are eddy current sensor arrays with single or dual rectangle drive configurations and linear arrays of inductive or magnetoresistive sensing elements. This presentation describes a range of applications for these sensors including stress/strain imaging/monitoring; corrosion imaging (internal and external) with and without coatings, insulation or fireproofing for piping, vessels and structures; and crack detection and depth measurement for fatigue and stress corrosion cracking. These solutions use multivariate inverse methods with precomputed databases called HyperLattices that enable estimation of multiple unknown properties of interest such as magnetic permeability, liftoff, pipe wall thickness, insulation thickness and weather jacket properties. The unique approach improves robustness to variations in field conditions (e.g. insulation sagging that causes substantial variation in insulation thickness around a pipe, or temperature variations that make inspection during operation challenging, or surface conditions that make crack or pit depth measurement more difficult). Handheld and larger portable instruments are also described that are uniquely capable of providing reliable imaging of multiple unknown properties (as required for reliable corrosion imaging through coatings or difficult surface conditions). These instruments provide simultaneous measurement at all channels in the arrays (no multiplexing) to enable improved image reliability and even rescaling or crack responses for cracks falling between channels. Furthermore, impedance at up to three frequencies is recorded simultaneously at every sensing element. This is essential for reliable correction for uncontrolled variations, such as changes in liftoff (sensor proximity to the surface) and/or magnetic permeability, to provide accurate pipe wall thickness measurement for example. Basic methods are described along with practical application results.

Mr Yohan Belanger

LynX Inspection Inc

Scientific Software Developper at Lynx Inspection and M.Sc. candidate in Electrical Engineering at Laval University in Quebec city, Canada. Part of the oNDuTy program for industrial training of graduate students in NDT. Proud owner of a B.Sc. in Physics. Working on new methods to acquire, clean and get the most information out of X-Ray images. Worked on GPU accelerated radiation physics simulations like volumic radiation dosimetry and image simulation. Experienced in radiation shielding computation and safety.

High Resolution SCC Depth Map in Pipeline Samples Using New X-Ray Imaging Techniques

Scientific Software Developper at Lynx Inspection and M.Sc. candidate in Electrical Engineering at Laval University in Quebec city, Canada. Part of the oNDuTy program for industrial training of graduate students in NDT. Proud owner of a B.Sc. in Physics. Working on new methods to acquire, clean and get the most information out of X-Ray images. Worked on GPU accelerated radiation physics simulations like volumic radiation dosimetry and image simulation. Experienced in radiation shielding computation and safety.

Co-Authors: Mr Luc Perron, Dr Xavier P V Maldague

Room: Grand E-F Ballroom | 4:00 PM Wednesday, April 3, 2019

Materials in pipelines are subjected to a series of stress and corrosive environments. These conditions eventually lead to stress corrosion cracking (SCC). Several NDT techniques already exist to detect and assess such cracks in the field, some being more efficient than others at providing accurate depth measurements. Such depth measurements will help decide between a low-cost repair and an expensive section replacement, but any new NDT method first needs to be evaluated in the lab before its gets deployed in the field. Validating that the method provides reliable results can hardly be done without a reliable ground truth. A new low cost X-Ray imaging method, involving scatter corrections and the physical aspects of SCC, was developed to generate high resolution 3D SCC depth maps of pipeline samples showing precise crack positions and depth measurements. This method could be used as a gold standard for evaluating other NDT techniques, such as ultrasound or eddy current, since X-Ray is almost always sure to yield a better resolution. We will discuss the challenges of making such measurements and the techniques used to overcome them using state of the art hardware and software.

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Non-destructive Direct Assessment of Mechanical Properties

Evaluating the strength of pipes has always been a decisive factor in the removal and replacement of vintage pipelines. Researches has been carried out in non-destructive inspection of in-service pipelines for various types of defects but when it comes to investigation of mechanical properties, there was no solution other than pipeline removal and destructive testing. This presentation features the noninvasive Hardness, Strength, and Ductility (HSD) Tester, developed by Massachusetts Material Technologies (MMT) to address issues in assessing key mechanical properties of base metals and welded seams on operating pipelines. Also included is the developing technology of the Non-destructive Toughness Tester (NDTT), which can provide fracture toughness values for different pipes.
The HSD is a portable device created for testing in-ditch pipelines and provides a highly accurate and experimentally validated assessment of the yield and ultimate tensile strength, along with a full stress-strain curve using the concept of frictional sliding, Recorded hardness values, and finite element analysis (FEA). Furthermore, this tester provides quality assessment and analysis of ERW long seams based on material classification algorithms.
The NDTT is an instrument that induces a micron-scale fracture mechanism, comparable to a standard crack tip opening displacement test. A wedge-shaped stylus that features a stretch passage is used to penetrate the surface of a sample by about 100 microns. As the material is torn, a micron-scale ligament is formed within the stretch passage, along with measurable crack propagation. Experimental validations and FEA are presented to support the effectiveness of this tester.

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The x-ray computed tomography (XCT) technique is a widely applicable and powerful non-destructive inspection modality for evaluation and analysis of geometrical and physical characteristics of materials, especially internal structures and features. XCT is applicable to metals, ceramics, plastics, and polymer and mixed composites, as well as components and materiel. The Army Research Laboratory (ARL) and its partners are currently investigating the use of cast FeMnAl steel alloy material in support of weight reduction in an Army Manufacturing Technology (ManTech) armor development program. Steel alloy FeMnAl has been identified as the key enabling materials technology to reduce the weight in the Abrams tank. A set of FeMnAl blocks each approximately 2” thick by 3” wide by 3” long, which had been sectioned from an industrially cast ingot (~12000 lbs.), were individually scanned by XCT using a conventional 450kV x-ray source and a solid state flat panel detector. Due mainly to the thickness of the blocks, as well as a desire to keep geometric unsharpness relatively small and the overall scan geometry (set up), the scans had a very low response at the detector through the FeMnAl blocks. With the calibrated detector response through air (i.e., around a block) at (85-90) percent the response through the block was only (5-10) percent. The XCT scanning parameters and overall protocol used to mitigate the very low intensity throughput and achieve acceptable scan image results will be discussed. Image processing methods used to segment porosity features in the FeMnAl blocks will also be discussed.

Dr Roberto Gil-Pita

University of Alcala

Roberto Gil-Pita (S’02-A’05-M’09) received the M.Eng. degree in telecommunication engineering and the Ph.D. degree (with hons.) in electrical engineering from the University of Alcalá, Madrid, Spain, in 2001 and 2006, respectively. From 2001, he has worked at the Signal Theory and Communications Department in the University of Alcalá, in the Applied Signal Processing research group. His research interests include pattern recognition and audio signal processing, focusing on residual thickness estimation in pipelines using ultrasound signals, emotion recognition and sound event detection. In these fields, he is author of more than 35 journal papers included in the Journal Citation Report, and around 100 conference papers. He is also project manager of several projects with public and private fundings, including the“Chair of modeling and processing of ultrasonic signals” (CATEDRA2007-001), funded by Innerspec Technologies Europe.

Roberto Gil-Pita (S’02-A’05-M’09) received the M.Eng. degree in telecommunication engineering and the Ph.D. degree (with hons.) in electrical engineering from the University of Alcalá, Madrid, Spain, in 2001 and 2006, respectively. From 2001, he has worked at the Signal Theory and Communications Department in the University of Alcalá, in the Applied Signal Processing research group. His research interests include pattern recognition and audio signal processing, focusing on residual thickness estimation in pipelines using ultrasound signals, emotion recognition and sound event detection. In these fields, he is author of more than 35 journal papers included in the Journal Citation Report, and around 100 conference papers. He is also project manager of several projects with public and private fundings, including the“Chair of modeling and processing of ultrasonic signals” (CATEDRA2007-001), funded by Innerspec Technologies Europe.

Defect sizing in pipeline inspection allows companies to determine when a pipe must be replaced, avoiding costly repairs in their equipment. To tackle this issue, Lamb ultrasonic waves generated through EMAT sensors allow thickness estimation without direct contact with the surface of the metallic material under investigation. However, the shape of the defect changes the behavior of the ultrasonic signals when they pass through the pipeline, and it is not easy to predict the amplitude and phase of the wave in function of the residual thickness. In recent studies the use of machine learning techniques applied to information extracted from signals sensed at different frequencies has been demonstrated to improve the accuracy of the estimation, but the use of multiple frequencies in general requires more complex sensing devices and more time. A possible way to tackle these disadvantages is the use of different modes sensed at a unique frequency, but in this case the selection of the coil and the inspection frequency becomes a critical aspect, since these different modes must be separable in the measurement, and this is not always the case.
In this paper, we present a theoretical and experimental study in which we analyze the selection of the coil and the frequency for multimodal thickness estimation. The objective is to determine the relationship between the performance of the estimator and the configuration of the sensing system. We use a double approach to the problem. First, a signal processing based theoretical framework is proposed. Second, simulations obtained by a Finite Element software are considered. Results demonstrate the suitability of the proposals, improving the estimation of the residual thickness.

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Mr David H Parker

Parker Intellectual Property Enterprises LLC

Bachelor of Electrical Engineering (74) and Masters in Physics (82) from Auburn University. Senior Member of OSA, Senior Member of SPIE, and Senior Member of IEEE. Also member of Coordinate Metrology Society, American Society for Precision Engineering, and American Society for Nondestructive Testing. First, or major, inventor of 15 US Patents and 1 pending applications--mostly metrology related. Also co-inventor of 14 additional US Patents and 3 pending applications. Published 10 journal articles and 15 conference papers. Worked in industry from 1974-1979. Worked in R&D, metrology, precision engineering, and intellectual property since 1982. Registered Professional Engineer and Registered Patent Agent. President, Parker Intellectual Property Enterprises, LLC.

Bachelor of Electrical Engineering (74) and Masters in Physics (82) from Auburn University. Senior Member of OSA, Senior Member of SPIE, and Senior Member of IEEE. Also member of Coordinate Metrology Society, American Society for Precision Engineering, and American Society for Nondestructive Testing. First, or major, inventor of 15 US Patents and 1 pending applications--mostly metrology related. Also co-inventor of 14 additional US Patents and 3 pending applications. Published 10 journal articles and 15 conference papers. Worked in industry from 1974-1979. Worked in R&D, metrology, precision engineering, and intellectual property since 1982. Registered Professional Engineer and Registered Patent Agent. President, Parker Intellectual Property Enterprises, LLC.

Co-Authors:

Room: Grand G Ballroom | 4:40 PM Wednesday, April 3, 2019

This is a companion paper to Opportunities for the use of electronic distance measurement instruments in nondestructive testing and structural health monitoring and implications for ASNT, which was presented at the 2018 ASNT Research Symposium. The earlier paper covered the background and capabilities of electronic distance measurement instruments, and in general how they could be used for nondestructive testing applications, which will not be repeated. This paper covers specific applications limited to pressure vessels, such as; boilers, receivers, nuclear reactor containment buildings, tank trucks, railway tank cars, storage tanks, ships, vacuum chambers, aircraft, spacecraft, and the like. An example experimental architecture and 3-D uncertainty analysis, using manufacturers instrument specifications and commercially available software (MicroSurvey® STAR*NET), is included for nondestructive testing of railway tank cars subjected to measured pressure and coupler forces. Structurally sound tank cars can be quickly, and quantifiably, identified by comparing the measured geometric performance of targeted cardinal points, under the pressures and forces, to finite element models (FEM), historical measurements of the car, or looking for salient characteristics such as; linearity, hysteresis, creep, symmetry, and the like—while defective tank cars will exhibit anomalous geometric performance, which requires further investigation. The net result would be that instead of releasing a tank car into service based on not finding a defect, it would be released into service based on measured structural performance.

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The strategic leadership of NDT research,
development and technology transfer is moving up a gear in the UK with a
stronger link between two well-established organisations: the British Institute
of NDT (BINDT) and the UK Research Centre for NDE (RCNDE). This strategic
partnership will be the main vehicle for increasing the coverage of industrial
sectors, technologies, geographical locations and the technology readiness levels
(TRL), including new technology qualification, technique validation, training
and certification. Government departments prefer to have one ‘go to’ leader in
a sector with whom they can consult and work to bring about step changes in
industrial practice. In the UK, the new strategic partnership will aim to link
with several other stakeholder organisations to provide that coherent
leadership. The challenges of the fourth industrial revolution (4IR) and the
NDT community’s response to those challenges, called ‘NDT 4.0’ by some, will
become one of the themes addressed by this strategic partnership. International
coverage will also be crucial and the strong international links already
established by BINDT and RCNDE will provide a route to increase global cooperation
on new technologies. Although this is early on in the partnership, this
presentation will cover the vision and seek feedback, particularly on the
mechanisms for international collaboration.

Orion Heatshield Bond Quality Inspection: Engineering a Technique

Presenting author(s):
Dr Joseph T Case

Co-Authors: Dr Shant Kenderian

Room: Grand E-F Ballroom | 9:00 AM Thursday, April 4, 2019

In recent years, there has been a concerted effort to inspect the bondline condition between thermal heatshield and composite substrate for the NASA Orion Space Capsule. Since it is to be used for manned space flight, the heatshield must protect the crew and the cargo during re-entry into the atmosphere. As a consequence of the extreme environment for which it is used, the heatshield must be fully inspected and qualified before use. The bondline has received considerable attention since unbonds of critical size or concentration can cause the bond to fail. It is required that the bondline inspection must be performed from the outer material layer and it must be one-sided. Many inspection techniques are ill-suited to inspect the heatshield. Moreover, one technique may not be capable to inspect all bond criteria: porosity, unbonds, and kissing unbonds. A kissing unbond is an unbond where two surfaces are in intimate contact yet no bond exists between these surfaces. Kissing unbonds are difficult or impossible to detect when using electromagnetic techniques like x-ray, Terahertz, or infrared techniques. Recently, an ultrasonic technique was demonstrated to detect these features and proper couplant, best transducer, and signal processing techniques were described. It has since been improved to become a freehand ultrasonic imaging technique such that the transducer is in contact with the outer surface for maximal signal. The technique will be described in detail regarding a protective surface between the transducer and the heatshield, the freehand scanning system, and image processing techniques used to form C-scans.

Lamb wave has been successfully used in structural health monitoring (SHM) of plate-like structures. One of the limitations of using Lamb waves is that there is not a framework to estimate coverage of sensor network used to excite and receive Lamb waves. An algorithm to calculate the coverage areas, in plate-like structures, of different sensor arrangement is developed using simplified wave-crack interaction models to address this problem. When it comes to crack detection in plate-like structures, a major question still worthy to research upon, is “what is the coverage area of different sensor patterns”. The main difficulty of finding the coverage area of different sensor arrangements is the interaction of wave and defects such as cracks is a function of numerous parameters. Analytical and semi-analytical solutions for this problem are quite computationally expensive and even in some cases unable to solve the problem. Hence, simplified wave reflection attenuation functions are proposed using several FEM models and used to predict sensor network coverage in structural health monitoring of plate-like structures.

Ultrasonic Inspection of Contact Bond

Presenting author(s):
Yong M Kim

Co-Authors: Mr Mark D Fuqua, Dr Dulip Samaratunga

Room: Grand E-F Ballroom | 9:20 AM Thursday, April 4, 2019

Contact bond, a glue-less bond by intermolecular forces, was inspected on silicon and silica samples by ultrasound. 25MHz pulse-echo scans revealed rich variations in bond-interface echoes. Distinctive arrival time of each echo identified its history of propagation-mode within medium and mode-conversion at boundary. The magnitude and the phase of each wavelet provided the local details about the bond condition and associated bond-force characteristics. Various bond samples, made of different composition in materials / crystal-orientations, bond processes and geometry, were inspected. The acoustic observations were analyzed, and their physical implications were projected. While acoustic propagation can be an effective inspection method for contact bond, its near zero-bond-thickness makes it to be an ideal system for the acoustic interaction study at material and crystal boundaries.

A virtual monitoring system based on a calibrated finite element model of an instrumented vertical lift steel gussetless truss bridge is developed to predict the bridge structural performance subject to multiple progressive damage scenarios at different zones throughout the structure. Since the gussetless connections behave structurally as semi-rigid joints, the interaction of bridge members is a complicated issue; therefore, the damage progress to the adjacent members could develop a weakened region in the structure which needs to be detected at the earliest possible stage. The evaluation procedure is based on the bridge dynamic response due to random excitations generated during lift operations. Using the information obtained from the accelerometers, a novel damage-index approach is introduced to account for damaged-induced variations in the system response and determine vulnerable zones to damage. Assuming that the average normalized energy stored in wavelet packets is highly correlated with damage effect on dynamic characteristics, a damage-sensitive feature is developed as an indicator of the structural impact of damage in each case. This paper illustrates the robustness of the wavelet transform approach for the local analysis of the collected data to extract dominant patterns associated with damage. The methodology proposed in this paper is beneficial to practitioners involved in structural condition assessment and can help bridge owners to gain a better insight into finding the regions which are most sensitive to damage.

Lamb Wave Technique for Adhesive Bonded Joint Inspection

Presenting author(s):
Dr Dulip Samaratunga

Co-Authors:

Room: Grand E-F Ballroom | 9:40 AM Thursday, April 4, 2019

Adhesive bond strength evaluation is a challenging problem in the NDE community. In the absence of reliable technique for bond strength inspection, it is extremely difficult to qualify adhesive bonded hardware and components for applications in the primary load paths. As a result, manufacturers are forced to implement additional fail-safe measures such as mechanical fasteners in conjunction with adhesive bonds. Consequently, the bonded joint designs loose key advantages such as lower weight, efficient load distribution, reduced number of parts count, etc. offered by such a material joining technique. This work presents an effort to utilize guided Lamb waves as a technique to predict bondline degradation. By nature, elliptical wave motion of Lamb waves can induce a relative normal/ shearing effect between plates at the interface of a bondline. Therefore, they are well suited for a type of inspection required in adhesive bond interfaces. Current research combines numerical simulation and laboratory testing to understand Lamb wave propagation in adhesive bonded plates. The numerical simulation involves the use of conventional and spectral finite element (FE) techniques to extract wave propagation behavior in both time and frequency domains. Selection of appropriate modes and key wave feature extraction are performed using numerical models. Lab testing is performed to verify and validate numerical simulations results. Test samples are made to simulate both adhesive and bond property variations since both adhesive and cohesive failures are possible in bonded joints.

The natural frequency of bridges is one of the most key dynamic parameters that represents the characteristics of the bridge and is most useful for many purposes. The identification of the frequency of bridges is a problem widely encountered in bridge engineering. Recently, authors have shifted to extract bridges' frequency, “indirectly”, from the responses of a passing vehicle, which has become known as “drive-by” inspection. “Drive-by” Bridge inspection approach has been developed dramatically since it has the advantage of convenience, economy, and safety. Previous studies have pointed out that the higher vehicle velocity amplifies the power for the bridge response in the spectrum of Fast Fourier Transform (FFT), which consequently implies easier extraction for the bridge frequency from the vehicle responses. However, as the speed increases, the vehicle spends lesser time on the bridge and consequently, the frequency resolution drops dramatically which result in a substantial error in the estimated frequency. This paper introduces a new frequency extraction technique based on the Hilbert Transform (HT), which is not restricted to frequency resolution so as to improve recognition of bridge frequency. In this paper, a closed-form solution for the bridge frequency is derived from the vehicle response, taking into account removing the effect of the vehicle velocity. Then numerical Vehicle-Bridge Interaction (VBI) model with a quarter car model is adopted to demonstrate the proposed approach.

Most of the available studies on fatigue damage quantification are focused on crack growth life and use crack length as the indicator. However, depending on the material, 50% to 90% of fatigue life is spent in crack initiation. Specifically, for rather more brittle materials, such as Aluminum 7075-T6, crack propagation is fast and it covers a short period of fatigue life. Since this material is commonly used in aerospace structures, developing a method to predict crack initiation time is of high importance and results in a better estimate of Remaining Useful Life (RUL) of critical structural components. In this study, two Non-Destructive Evaluation (NDE) techniques, namely Acoustic Emission (AE) and Digital Image Correlation (DIC) are used to measure characteristics of notched dog-bone specimen made of Aluminum 7075-T6. AE waveforms related to crack initiation are detected and their information entropy, as an indicator of fatigue damage, are measured. DIC, on the other hand, is used to measure plastic strain generating around the notch during fatigue load. AE information entropy data and strain measurement from DIC are used to depict a better image of changes in the material during crack initiation life.

Including Environmental and Vertical Lift Excitations for Structural Condition Assessment of a Gussetless Truss Bridge

Presenting author(s):
Ms Maryam Mashayekhizadeh

Co-Authors: Dr Erin Santini Bell

Room: Grand G Ballroom | 10:00 AM Thursday, April 4, 2019

Structural condition assessment program for civil infrastructure aims to inform about the health condition of the structure for serviceability and safety assessment. An efficient monitoring program requires the optimum selection of the sensors in terms of type, number and the appropriate location to represent the real-time performance of the structure with respect to anticipated structural excitations. Recent advances in the design and application of the bridges serving multiple transportation tasks such as movable bridges motivated this work to develop appropriate monitoring programs for these types of bridges to inform on the performance of the bridge. The complex lift mechanism in the vertical lift bridges has a significant influence on the design and performance of the bridge’s vertical lift tower, which is less-studied due to limited available data. Understanding the healthy condition of the bridge’s tower under the lift operation aides to determine the subsequent variation in lift mechanism performance that may indicate a reduction in condition and need to inspect the system. This study aims to investigate the structural performance of the lift’s tower under the lift action and considering the environmental excitation. The case study is the Memorial Bridge, a vertical lift bridge in Portsmouth, NH which has a long-term monitoring plan for the fixed span and the lifting tower. In this study, the structural data collected at the bridge’s vertical tower during the lift actions over a year, is used to assess the impact of the variable environmental conditions. Predicting the structural response excited by the lift action is performed through a statistical analysis of the collected data. The acquired response can help the bridge managers for the decision-making protocol to schedule inspections and maintenance efforts and minimize the downtime of the bridge.

Ultrasonic Testing Beyond Flaw Detection

Presenting author(s):
Dr Hormoz Ghaziary

Co-Authors:

Room: Grand E-F Ballroom | 10:20 AM Thursday, April 4, 2019

The relationship between ultrasound transmission characteristics and the mechanical properties of the medium in which it propagates has been well understood and often used in laboratory environment. 21th century technology enables us to acquire, store, and process large amounts of data which in turn allows us to observe the distribution of mechanical properties on actual components and semi-finished materials. This paper describes two ultrasonic characterization techniques usable in aerospace environment. These are both related to characterization of rolled aluminum plates used by the aerospace industry for machining of monolithic components. One technique is the use of ultrasound to project the content and distribution of small pores which are not detectable by conventional ultrasonic flaw detection techniques and yet negatively influence the fatigue resistance of the material. The second technique is the use of ultrasound to locate regions of a plate with excessive stress which may lead to deflection and deformation during the machining process. In this technique Ultrasonic transmission properties are used to map material elastic constant and project machining deflection at areas of interest.

Mr Saman Farhangdoust

Florida International University

Mr. Saman Farhangdoust is a graduate research assistant at Accelerated Bridge Construction University Transportation Center (ABC – UTC) and pursuing his Ph.D. in Civil Engineering at Florida International University. As a multidisciplinary engineer, he is currently working on Infrastructure Systems Design, Structural Health Monitoring (SHM) of Composite Structures, Nondestructive Evaluation (NDE), and Smart Bridge Monitoring projects. Saman is an active member of ASME, ACI, ASNT, and ASCE. He has been author/co-author of more than 20 papers in international journals and refereed conference proceedings in the area of Structural Health Monitoring (SHM) and Nondestructive Evaluation (NDT).

Mr. Saman Farhangdoust is a graduate research assistant at Accelerated Bridge Construction University Transportation Center (ABC – UTC) and pursuing his Ph.D. in Civil Engineering at Florida International University. As a multidisciplinary engineer, he is currently working on Infrastructure Systems Design, Structural Health Monitoring (SHM) of Composite Structures, Nondestructive Evaluation (NDE), and Smart Bridge Monitoring projects. Saman is an active member of ASME, ACI, ASNT, and ASCE. He has been author/co-author of more than 20 papers in international journals and refereed conference proceedings in the area of Structural Health Monitoring (SHM) and Nondestructive Evaluation (NDT).

Co-Authors: Mr Armin Mehrabi

Room: Grand G Ballroom | 10:20 AM Thursday, April 4, 2019

Accelerated Bridge Construction (ABC) is the method for building and rehabilitating bridge construction aimed at reducing on-site activities, traffic interruptions, and cost. In general, ABC uses precast elements for either bridge superstructure or substructures which are fabricated on site or away, and moved to the bridge site and installed in place. Full-depth precast concrete deck panels are a key element of ABC superstructures for which there is more potential for defects to occur during construction, or develop later during the life of the structure. Despite numerous investigations on the causes of defects for bridge superstructures in general, an attempt for constructing a rational relationship between observed or presumed defects in ABC full-depth precast concrete deck panels, in another word defect etiology, is lacking. According to the defect etiology, most of the defects and damages in ABC deck can be caused by one or more of the issues with; Design, Material, Workmanship, Shrinkage, Mechanical and Environmental conditions, each of which will be methodically analyzed in the presented paper. In a paper presented previously, the most promising Nondestructive testing (NDT) methods in health monitoring and inspection of the ABC were identified and characterized. The current paper attempts to introduce a reliable examination, and accordingly comparison among the selected NDT techniques in ABC taking into account the defect etiology associated with Full-Depth Precast Concrete Deck Panels.

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Dr Ahmed Elhattab

Southern Company Services

A Professional Structural Engineer with 9+ years of experience in structural engineering profession. Designed and led 40+ engineering projects with total values exceeds $220M USD. Led several Bridge Structural Health Monitoring projects for NSF, NCHRP, UTC, and ALDOT. My research is oriented towards integrating remote sensing and computational algorithms to develop cyberinfrastructure systems, perform data driven bridge health assessment. I published over 15 articles in the Structural Health Monitoring Field.

A Professional Structural Engineer with 9+ years of experience in structural engineering profession. Designed and led 40+ engineering projects with total values exceeds $220M USD. Led several Bridge Structural Health Monitoring projects for NSF, NCHRP, UTC, and ALDOT. My research is oriented towards integrating remote sensing and computational algorithms to develop cyberinfrastructure systems, perform data driven bridge health assessment. I published over 15 articles in the Structural Health Monitoring Field.

Co-Authors: Mr Nasim Uddin, Mr Eugene OBrien

Room: Grand E-F Ballroom | 10:40 AM Thursday, April 4, 2019

Current inspection practices specially for aircraft industry require a tear-down inspection of major frame elements to allow early detection of incipient cracks and flaws. Inspections are scheduled through the operation life of the aircraft to ensure safety, which excessively increase the cost of operation. Therefore, recently there has been an impetus to move from scheduled base inspection towards condition base monitoring. Vibration Based Monitoring has been used for decades as a robust tool to identify and assess cracks and flaws. However, damage needs to be sever in order to induce a significant change to the recorded vibration, otherwise the signature of the damage will be swamped by the background noise. The research effort in this article is devoted to develop a quick and efficient incipient damage detection technique by using few acceleration records from the aircraft frame. The technique is founded on developing a specialized Signal Filter using Stochastic Resonance phenomenon that has the capacity to amplify and extract feeble vibrations such as the crack vibrations. Conventional filters extract the signal by blocking and attenuating the noise, therefore weak signals (such as crack signals) are weakened and destroyed in the denoising process. Stochastic Resonance is a model for weak response detection whereby feeble responces are amplified and extracted by using rather than suppressing the noise in the signal. The developed filter has the capacity to track the dynamic characteristics of the crack to infer when the crack present in the aircraft frame. The study will investigate the fidelity of the proposed approach using a Finite Element Model for an aircraft vertical tail. Two source of vibration will be examined: a) single hammer knock, and b) using a Piezoceramic Exciter.

Prestressed concrete girders often serve as critical components in of structure systems. Failure of a prestressed concrete beam could result in severe structure damage which could lead to catastrophic collapse of a structure. Acoustic emission (AE) monitoring is considered to be an effective way to evaluate the performance of a structure component and access its level of damage under different levels of loading. For this study, a prestressed concrete I-section beam was tested under incremental cyclic third-point bending load with continuous AE monitoring. The objective of this work is to qualify and quantify damage accumulation of the prestressed concrete beam using AE signatures and correlate these AE signatures with strain measurement as well as the actual crack patterns observed during the loading cycles. The experimental results indicated that damage level of the prestressed beam was in agreement with two AE parameters load ratio and calm ratio based on the phenomena of Kaiser effect and Felicity effect. Meanwhile, AE b-value analysis based on amplitude distribution of AE hits was carried out and verified to be a potential evaluation method of detecting the fracture development of the prestressed beam. The analytical method provides insight on monitoring methodologies implementable for monitoring of field structures.

Mr Gary S LeMay

Spirit AeroSystems

Gary LeMay is a Research and Development
Engineer for Spirit AeroSystems Inc. in Wichita, Kansas. Gary translates
engineering and scientific principles from preliminary ideas, through
technology readiness levels, to maturity in a relevant environment. Gary is a
Principal Investigator and has led multiple internal Research and Development
projects to improve inspection rates and lower costs by developing new and
advanced NDE methods and technologies. Gary has a Master of Science degree in
Mechanical Engineering from Wichita State University and is currently pursuing
his PhD with emphasis in statistical process control, data mining, and
analytics.

A New Method for Ultrasonic Detection of Peel Ply at the Bondline of Out-Of-Autoclave Composite Assemblies

Gary LeMay is a Research and Development
Engineer for Spirit AeroSystems Inc. in Wichita, Kansas. Gary translates
engineering and scientific principles from preliminary ideas, through
technology readiness levels, to maturity in a relevant environment. Gary is a
Principal Investigator and has led multiple internal Research and Development
projects to improve inspection rates and lower costs by developing new and
advanced NDE methods and technologies. Gary has a Master of Science degree in
Mechanical Engineering from Wichita State University and is currently pursuing
his PhD with emphasis in statistical process control, data mining, and
analytics.

Co-Authors:

Room: Grand E-F Ballroom | 1:00 PM Thursday, April 4, 2019

Out-of-autoclave materials have long been an established material system for secondary structural applications; however, recent advancements in material properties allow for more advanced structural applications. Even though certain out-of-autoclave properties have achieved parity with autoclaved cured materials, out-of-autoclave materials are cured at reduced temperatures and pressures resulting in less compaction and homogeneity. The consequence is extraneous ultrasonic signals, due to internal reflections and refractions that cause attenuation, potentially masking defects leading to unidentifiable indications. Advanced algorithms were developed to improve the signal to noise ratio between constituents of similar acoustic impedance in bonded out-of-autoclave carbon fiber reinforced polymer assemblies. Conventional ultrasonic nondestructive testing techniques and analysis software cannot consistently achieve signal to noise ratios that meet quantifiable rejection thresholds of accurately sized peel ply inserts at the bonded interface of composite assemblies. Ultrasonic pulse echo with full waveform capture was used to inspect a reference standard with peel ply inserts placed between the adhesive and three-dimensional-woven fabric preform. The ultrasonic signal was produced by a 64 element array transducer with a central frequency of 2.8 MHz. Waveform post-acquisition analysis with post processing software was used to analyze and enhance the signal response between the peel ply and the bondline resulting in the final algorithm. To verify the results, the signal to noise ratio of each insert was calculated for both the raw and processed data. As the measure of detectability, the method relies on principles of statistical measurement to provide an industry standard signal to noise response of 3:1.

Mr Xingxing Zou

Missouri University of Science & Technology

Xingxing Zou is a PhD student at Department of Civil Engineering of Misssouri University of Science and Technology since Augest 2016. He got his master degree of Civil Engineering in Southeast University, Nanjing, China. His current advisor is Dr. Lesley Sneed. His PhD research is about the bonding behavior of advanced composites strengthened concrete structures, especially bridges.

Xingxing Zou is a PhD student at Department of Civil Engineering of Misssouri University of Science and Technology since Augest 2016. He got his master degree of Civil Engineering in Southeast University, Nanjing, China. His current advisor is Dr. Lesley Sneed. His PhD research is about the bonding behavior of advanced composites strengthened concrete structures, especially bridges.

Fiber reinforced polymer (FRP) composites have been widely used as externally bonded reinforcement to strengthen concrete structures. However, interfacial debonding between the FRP and concrete substrate, which occurs when the shear stress exceeds the bond strength, can inhibit composite action. Such damage cannot be identified visually since it occurs within a thin layer of concrete beneath the composite bonded area. Active microwave thermography (AMT), an integrated nondestructive testing and evaluation (NDT&E) technique that utilizes a microwave heat excitation and subsequent thermal monitoring via a thermal camera, has shown promise in detecting embedded voids and defects in FRP composites. In this study, carbon FRP (CFRP)-concrete joints were tested in direct shear, and AMT was used to monitor the surface of the CFRP in an attempt to study interfacial damage. Strain profiles along the composite bonded length were used to determine the interfacial cohesive material law, which relates the interfacial shear stress and relative slip between the CFRP and the concrete. Changes in the CFRP surface thermal profile correlated well with abrupt changes in the applied load versus loaded end displacement response, which indicated the development of localized damage within the concrete. A strong correlation between the CFRP-concrete interfacial slip and the CFRP outer surface temperature increase was observed, which indicates that initiation and propagation of debonding along the CFRP-concrete interface can be detected by AMT.
This work has been partially supported by the National Science Foundation Electrical, Communication, and Cyber Systems (ECCS) Award 1609470, “A Multi-Physics-Based Approach to Active Microwave Thermography”.

As industrial manufacturing pursues toward light and excellent performance, the use and promotion of composite materials have become increasingly popular particularly in the aerospace and automotive industries. Understanding the mechanical properties of composites can provide sufficient information for effective use and predict specific damages for which could cause obvious changes in the elastic constants.
This presentation will deal with the use of ultrasonic guided waves for the identification of the elastic constants laminated composite. In particular, the Semi-Analytical Finite Element (SAFE) method is used to predict dispersion curves for a set of five independent properties (E_11,E_22,ν_12,G_12,ν_23) of the individual laminae. An optimization procedure based on Simulated Annealing is then used to iterate the property values so as to obtain a match between the predicted phase velocity dispersion curves and the actual dispersion curves for the given laminate. This results into the identification of the lamina properties.
The role of the multiple guided modes (specifically A_0,SH_0,S_0) on the convergence of the property identification is analyzed in detail. Proof of principle results will be shown for the property identification of Carbon-Epoxy composite laminates of various lay-ups, including anisotropic lay-ups and quasi-isotropic lay-ups.

The corrosion of reinforcement is a leading cause of structural deficiency and the reduction of a structure’s service life. To enhance structural performance and ensure that each structure meets its intended design life, it is important that corrosion be mitigated and monitored. Epoxy coated rebar (ECR) was first introduced in 1973 and has since been implemented in bridge decks by at least 41 state transportation departments due to the increased usage of deicing salts and the related corrosion problems. It has been observed in some case studies that the inclusion of ECR either increased the risk of corrosion or that it did not improve the corrosion resistance of the bridge deck. Due to an increasing demand for more sustainable structures, a method to properly test and evaluate the condition of ECR is necessary to determine the service life and to propose an adequate maintenance or rehabilitation program.
The half-cell potential is the most common test for in-situ corrosion assessment, but only provides insight on the probability of corrosion and must be supplemented by other forms of non-destructive testing (NDT). In this study, resistivity of the surrounding concrete will supplement half-cell potential. This proposed methodology will be performed on 9 inch thick reinforced bridge-deck slabs from I-35 in Oklahoma. The bridge was constructed with both standard and epoxy coated rebar; a corrosion assessment of the standard rebar will be used for comparison and validation of the ECR assessment. The experimental results will reveal the accuracy of the test methodology compared to standard rebar assessment and determine if it is adequate to evaluate the probability of corrosion in bridge decks with ECR.

Digital Laser Speckle Image Correlation for the Determination of Repair Compliance within GFRP

Presenting author(s):
Dr Tsuchin Philip Chu

Co-Authors: Mr Albert Anthony Lyles

Room: Grand E-F Ballroom | 1:40 PM Thursday, April 4, 2019

This research discusses the nondestructive evaluation of a honeycomb-backed glass fiber reinforced polymer (GFRP) aircraft panel, by use of the optical method known as Digital Laser Image Correlation (DiLSIC). This approach uses laser projected onto the test subject, to create speckles, as a replacement for traditional artifact speckles used in white light digital image correlation (DIC). The main purpose of this research is to detect subsurface embedded repairs in the GFRP aircraft panel and determine the level of proper repair compliance between two repairs. One being a compliant ready for use repair and the other a noncompliant, not ready for use repair. A thermal load is applied to the defect panel and this technique calculates subsurface strain to produce a strain map that can be used to differentiate a compliant repair from a noncompliant repair. Unlike conventional white light artifact speckle DIC, this technology uses no post manufacturing artifact speckles applied to the surface of the subject. DiLSIC utilizes the reflective properties of a coherent laser reflection caused by surface roughness inherently on the surface of the target. This new variation of DIC shows high resolution and accuracy. The DiLSIC system measured an observable difference between the two different repairs. DiLSIC shows great promise for in the field applications and for situations that traditional DIC is not an option for usage due to the inability of the addition of physical artifact speckles post installation, or while in use. DiLSIC is an exciting method of defect detection and quantification for use in locations that have not been viable options in the past.

The Full-Matrix-Capture (FMC) technique offers new opportunities for ultrasonic imaging of concrete structures. Its real-time imaging capability is successfully used for quality assurance in construction industry. Although, the available testing instruments on the market implement the principle of linear transducer array with its two-dimensional reconstruction of B-Scan images according to Synthetic Aperture Focusing Technique (SAFT) principle.
The Dry-Point-Contact transducers utilized in commercially available instruments for concrete testing with their matrix-like layout offer direct opportunity to implement three-dimensional Full-Matrix-Capture (FMC) data acquisition cycle. The obtained data can be in real-time processed in 3D-SAFT reconstruction and visualization of inspection results.
In the present contribution experimental results of 3D-FMC data processing and visualization performed on real concrete inspection objects are presented and the advantages of true 3D tomography in respect to improved information content and easiness of result interpretation is discusses.

Progress in Autonomous Inspections using Collaborative Robots

Presenting author(s):
Dr Patrick H Johnston

Co-Authors: Mr Elliott K Cramer

Room: Grand E-F Ballroom | 2:00 PM Thursday, April 4, 2019

In recent years, the aerospace community has increased the use of composites in aeronautic and space vehicles. As demonstrated by the Boeing 787’s use of composites, NASA’s Composite Crew Module and liquid hydrogen cryogenic tanks, there is a push toward the use of composites for primary structural components. As these composite structures become larger and more complex, nondestructive evaluation (NDE) techniques capable of quantifying and characterizing damage are needed. Current research at NASA Langley Research Center is investigating the use of collaborative robots (COBOTS) for autonomous inspections. A collaborative robot is a robot intended to physically interact with humans in a shared workspace. In most cases though, robotic implementation simply replaces the manual movement of an inspection transducer or system over the structure, with an automated one. While this implementation achieves some modest improvements in inspection efficiency, a continuously moving inspection system has the potential to further decrease inspection times. This paper will present details of a dual COBOT implementation of line scan thermography for the inspection of a complex geometry, composite aircraft fuselage. Line scan thermography is an inspection technique has proven to be a successful means of rapidly scanning large areas of aircraft fuselage. The technique involves the movement of a line heat source across the outer surface of a large structure followed by an infrared imager at a fixed distance behind the heater. Images of defects in the structure under inspection are reconstructed from measurements of the induced surface temperature variations. An overview of the line scan thermography technique along with the COBOT implementation, details and inspection results will be presented.

Resistivity Behavior of Concrete Mixtures with Included Supplementary Cementitious Materials

Presenting author(s):
Mr Cody Shults

Co-Authors: Ms Julie Ann Hartell

Room: Grand G Ballroom | 2:00 PM Thursday, April 4, 2019

Surface resistivity is a great nondestructive evaluation tool which may be used on a structure to assess the quality of the concrete in-situ along with the likelihood of an ongoing reinforcement corrosion durability issue. However, it is currently unknown to what extent mixture design parameters will affect a measurement. The inclusion of supplementary cementitious materials (SCMs) in a concrete mixture will affect the results of surface resistivity tests conducted on that concrete mixture. This study was conducted in order to better understand the effect that common SCM replacement ratios will have on the surface resistivity results. This is an important relationship to understand if surface resistivity is to be adequately used in the field for concrete integrity interpretation. In this study, control mixes of set water-to-cementitious material ratios (0.40, 0.45, 0.50) were cast along with the same mixes with the inclusion of three different SCMs at selected cement replacement ratios. The SCM replacements studied included class-C fly ash at 5%, 10%, and 20% weight replacement; blast furnace slag at 5% and 40% weight replacement; and silica fume at 2% and 8% weight replacement. Also studied were the effects of two common admixtures that are typically used in the industry (an air entraining agent and a high-range water-reducer). The surface resistivity values of the cast cylinders from each mixture were taken at 1, 3, 7, 14, 21, 28, and 56 days. Based on obtained values and trends for the potential gain in resistivity in time, a statistical evaluation between sample means and differences was performed to determine influential parameters and their extent on a measurement’s value. In turn, this will aid with potential result interpretation when conducting this method in the field.

When manufacturing or repairing structures with composite laminate materials, internal features of overlapping fiber plies and ply orientation misplacement can occur. These composite processing steps will influence material characteristics of the component and likely change the inspection results. As part of the quality assurance process, nondestructive evaluation methods are needed for inspecting laminated composites to ensure the materials are undamaged and meet the design parameters required for the structure’s intended application. The present study considers laser shearography and roller probe ultrasound techniques for inspecting laminated composites with overlapping fiber plies. The samples used in this study were designed and manufactured such that two different laminate thicknesses and three designs of overlapping fiber plies were considered. Each of the samples was manufactured using an 8-harness satin carbon fiber weave fabric and a thermoset resin. The benefits and limitations of using these two nondestructive inspection methods for assessing carbon fiber reinforced laminated composites with internal ply overlaps will be presented.

CFRP components from the point of view of the in-process quality assurance and ultrasonic material testing pose a challenging task due to its specific acoustic properties and complex shape. Constructional and productional optimization of CFRP parts show a tendency to more and more integrated and geometrically complex design with numerous three-dimensional curved surfaces and versatile material mixtures.
Apart of those traditional“ challenges in some cases, the „king-size“ dimensions of CFRP aircraft components rise additional challenges for their ultrasonic testing and require specific solutions in respect to visualization of large-scale structures and handling of big data.
In the present contribution advanced methods for ultrasonic testing of large parts are exemplified by automated inspection of the rocket fuel tank made of CFRP. Fast data acquisition and real-time adaptive TFM image reconstruction have been implemented on partially strongly varying geometry. Three-dimensional volume reconstruction and visualization allow fast evaluation of inspection results despite tremendous dimensions.

Pull-off Test

Presenting author(s):
Mr Evan Karunaratne

Co-Authors: Ms Julie Ann Hartell, Dr Norbert Delatte

Room: Grand G Ballroom | 2:40 PM Thursday, April 4, 2019

The pull-off test or “bond-test” is considered as a nondestructive testing method generally used in the concrete repair industry to measure the adhesion between a coating and a concrete’s surface. The method allows for better quality control of bond performance when applying coatings or overlays on concrete, in addition to providing a more complete understanding of the applied coating and/or substrate strength. In particular, the strength values obtained from this test let the user know if there is an issue regarding the coating being tested or the substrate surface preparation leading to disbondment. For example, the moisture content of a concrete material prior to application of a coating causing insufficient adhesion. For this study, differences between concrete surface preparations and coating materials are investigated to better understand field performance of the concrete repair system and propose adequate repair methods to ensure optimal performance. Through testing of various epoxy and polyaspartic polyuria based coatings, the pull-off test was used to better understand the bonding performance between the coating and the surface of the concrete. In addition to this, the influence of internal moisture and surface moisture conditions along with coating layer thickness were evaluated to see how these affected the bond strength between the concrete and the coating. It was determined that the internal moisture of concrete can affect the bond performance of the coating material even if the surface moisture was low at time of application. Also, the test may not be suitable for determining the performance of a coating if its thickness is a parameter of concern.